From ccdda39e78fc24d7cf5e2ea610f1faf611aa5197 Mon Sep 17 00:00:00 2001
From: BruebachL <44814898+BruebachL@users.noreply.github.com>
Date: Sat, 13 Dec 2025 15:17:55 +0100
Subject: [PATCH] Deck format legality checker (#6166)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* Deck legality checker.

Took 51 seconds

Took 1 minute

Took 1 minute

Took 5 minutes

Took 3 minutes

* Adjust format parsing.

Took 8 minutes


Took 3 seconds

* toString() the xmlName

Took 4 minutes

* more toStrings()

Took 5 minutes

* Comments

Took 3 minutes

* Layout

Took 2 minutes

* Layout part 2: Electric boogaloo

Took 59 seconds

* Update cockatrice/src/interface/widgets/visual_database_display/visual_database_display_format_legality_filter_widget.cpp

Co-authored-by: RickyRister <42636155+RickyRister@users.noreply.github.com>

* Move layout.

Took 4 minutes


Took 10 seconds

* Emit deckModified

Took 6 minutes

* Fix qOverloads

Took 4 minutes

* Fix qOverloads

Took 12 seconds

* Consider text and name in a special way.

Took 11 minutes

* Adjust "Any number of" oracle text

Took 5 minutes

* Store allowedCounts by format

Took 15 minutes

Took 6 seconds

* Only restrict vintage.

Took 2 minutes

* Adjust for DBConverter.

Took 6 minutes

---------

Co-authored-by: Lukas Brübach <Bruebach.Lukas@bdosecurity.de>
Co-authored-by: RickyRister <42636155+RickyRister@users.noreply.github.com>
---
 cockatrice/CMakeLists.txt                     |   1 +
 .../deck_editor_deck_dock_widget.cpp          |  67 +++++-
 .../deck_editor_deck_dock_widget.h            |   3 +
 .../deck_editor/deck_list_style_proxy.cpp     |   3 +-
 .../tabs/api/archidekt/tab_archidekt.cpp      |   4 +-
 ..._display_format_legality_filter_widget.cpp | 205 ++++++++++++++++++
 ...se_display_format_legality_filter_widget.h |  43 ++++
 ...tabase_display_main_type_filter_widget.cpp |   2 +-
 ...ual_database_display_set_filter_widget.cpp |   2 +-
 ...atabase_display_sub_type_filter_widget.cpp |   2 +-
 .../visual_database_display_widget.cpp        |   2 +
 .../visual_database_display_widget.h          |   2 +
 .../visual_deck_editor_sample_hand_widget.cpp |   4 +-
 ...ual_deck_storage_quick_settings_widget.cpp |   6 +-
 dbconverter/src/main.h                        |  72 +++++-
 libcockatrice_card/CMakeLists.txt             |   2 +
 .../libcockatrice/card/card_info.h            |   3 +
 .../card/database/card_database.cpp           |   5 +
 .../card/database/card_database.h             |   4 +
 .../card/database/card_database_loader.cpp    |   3 +-
 .../card/database/card_database_querier.cpp   |  23 ++
 .../card/database/card_database_querier.h     |   2 +
 .../database/parser/card_database_parser.h    |   6 +-
 .../card/database/parser/cockatrice_xml_3.cpp |   5 +-
 .../card/database/parser/cockatrice_xml_3.h   |   3 +-
 .../card/database/parser/cockatrice_xml_4.cpp | 179 ++++++++++++++-
 .../card/database/parser/cockatrice_xml_4.h   |   4 +-
 .../card/format/format_legality_rules.cpp     |  53 +++++
 .../card/format/format_legality_rules.h       |  73 +++++++
 .../libcockatrice/deck_list/deck_list.cpp     |  10 +-
 .../libcockatrice/deck_list/deck_list.h       |  12 +-
 .../tree/abstract_deck_list_card_node.h       |   6 +
 .../deck_list/tree/deck_list_card_node.h      |  19 +-
 .../models/deck_list/deck_list_model.cpp      | 105 ++++++++-
 .../models/deck_list/deck_list_model.h        |  14 ++
 oracle/src/oracleimporter.cpp                 |  72 +++++-
 oracle/src/oracleimporter.h                   |   1 +
 37 files changed, 987 insertions(+), 35 deletions(-)
 create mode 100644 cockatrice/src/interface/widgets/visual_database_display/visual_database_display_format_legality_filter_widget.cpp
 create mode 100644 cockatrice/src/interface/widgets/visual_database_display/visual_database_display_format_legality_filter_widget.h
 create mode 100644 libcockatrice_card/libcockatrice/card/format/format_legality_rules.cpp
 create mode 100644 libcockatrice_card/libcockatrice/card/format/format_legality_rules.h

diff --git a/cockatrice/CMakeLists.txt b/cockatrice/CMakeLists.txt
index dec1b3d62..c9fa80e6b 100644
--- a/cockatrice/CMakeLists.txt
+++ b/cockatrice/CMakeLists.txt
@@ -202,6 +202,7 @@ set(cockatrice_SOURCES
     src/interface/widgets/utility/sequence_edit.cpp
     src/interface/widgets/visual_database_display/visual_database_display_color_filter_widget.cpp
     src/interface/widgets/visual_database_display/visual_database_display_filter_save_load_widget.cpp
+    src/interface/widgets/visual_database_display/visual_database_display_format_legality_filter_widget.cpp
     src/interface/widgets/visual_database_display/visual_database_display_main_type_filter_widget.cpp
     src/interface/widgets/visual_database_display/visual_database_display_name_filter_widget.cpp
     src/interface/widgets/visual_database_display/visual_database_display_set_filter_widget.cpp
diff --git a/cockatrice/src/interface/widgets/deck_editor/deck_editor_deck_dock_widget.cpp b/cockatrice/src/interface/widgets/deck_editor/deck_editor_deck_dock_widget.cpp
index 08ebf23ba..268a13d5f 100644
--- a/cockatrice/src/interface/widgets/deck_editor/deck_editor_deck_dock_widget.cpp
+++ b/cockatrice/src/interface/widgets/deck_editor/deck_editor_deck_dock_widget.cpp
@@ -124,6 +124,12 @@ void DeckEditorDeckDockWidget::createDeckDock()
     quickSettingsWidget->addSettingsWidget(showBannerCardCheckBox);
     quickSettingsWidget->addSettingsWidget(showTagsWidgetCheckBox);
 
+    formatLabel = new QLabel(this);
+
+    formatComboBox = new QComboBox(this);
+    formatComboBox->addItem(tr("Loading Database..."));
+    formatComboBox->setEnabled(false); // Disable until loaded
+
     commentsLabel = new QLabel();
     commentsLabel->setObjectName("commentsLabel");
     commentsEdit = new QTextEdit;
@@ -208,13 +214,16 @@ void DeckEditorDeckDockWidget::createDeckDock()
     upperLayout->addWidget(commentsLabel, 1, 0);
     upperLayout->addWidget(commentsEdit, 1, 1);
 
-    upperLayout->addWidget(bannerCardLabel, 2, 0);
-    upperLayout->addWidget(bannerCardComboBox, 2, 1);
+    upperLayout->addWidget(formatLabel, 2, 0);
+    upperLayout->addWidget(formatComboBox, 2, 1);
 
-    upperLayout->addWidget(deckTagsDisplayWidget, 3, 1);
+    upperLayout->addWidget(bannerCardLabel, 3, 0);
+    upperLayout->addWidget(bannerCardComboBox, 3, 1);
 
-    upperLayout->addWidget(activeGroupCriteriaLabel, 4, 0);
-    upperLayout->addWidget(activeGroupCriteriaComboBox, 4, 1);
+    upperLayout->addWidget(deckTagsDisplayWidget, 4, 1);
+
+    upperLayout->addWidget(activeGroupCriteriaLabel, 5, 0);
+    upperLayout->addWidget(activeGroupCriteriaComboBox, 5, 1);
 
     hashLabel1 = new QLabel();
     hashLabel1->setObjectName("hashLabel1");
@@ -263,6 +272,46 @@ void DeckEditorDeckDockWidget::createDeckDock()
 
     refreshShortcuts();
     retranslateUi();
+
+    connect(CardDatabaseManager::getInstance(), &CardDatabase::cardDatabaseLoadingFinished, this,
+            &DeckEditorDeckDockWidget::initializeFormats);
+
+    if (CardDatabaseManager::getInstance()->getLoadStatus() == LoadStatus::Ok) {
+        initializeFormats();
+    }
+}
+
+void DeckEditorDeckDockWidget::initializeFormats()
+{
+    QMap<QString, int> allFormats = CardDatabaseManager::query()->getAllFormatsWithCount();
+
+    formatComboBox->clear(); // Remove "Loading Database..."
+    formatComboBox->setEnabled(true);
+
+    // Populate with formats
+    formatComboBox->addItem("", "");
+    for (auto it = allFormats.constBegin(); it != allFormats.constEnd(); ++it) {
+        QString displayText = QString("%1").arg(it.key());
+        formatComboBox->addItem(displayText, it.key()); // store the raw key in itemData
+    }
+
+    if (!deckModel->getDeckList()->getGameFormat().isEmpty()) {
+        deckModel->setActiveFormat(deckModel->getDeckList()->getGameFormat());
+        formatComboBox->setCurrentIndex(formatComboBox->findData(deckModel->getDeckList()->getGameFormat()));
+    } else {
+        // Ensure no selection is visible initially
+        formatComboBox->setCurrentIndex(-1);
+    }
+
+    connect(formatComboBox, QOverload<int>::of(&QComboBox::currentIndexChanged), this, [this](int index) {
+        if (index >= 0) {
+            QString formatKey = formatComboBox->itemData(index).toString();
+            deckModel->setActiveFormat(formatKey);
+        } else {
+            deckModel->setActiveFormat(QString()); // clear format if deselected
+        }
+        emit deckModified();
+    });
 }
 
 ExactCard DeckEditorDeckDockWidget::getCurrentCard()
@@ -466,6 +515,12 @@ void DeckEditorDeckDockWidget::syncDisplayWidgetsToModel()
 void DeckEditorDeckDockWidget::sortDeckModelToDeckView()
 {
     deckModel->sort(deckView->header()->sortIndicatorSection(), deckView->header()->sortIndicatorOrder());
+    deckModel->setActiveFormat(deckModel->getDeckList()->getGameFormat());
+    formatComboBox->setCurrentIndex(formatComboBox->findData(deckModel->getDeckList()->getGameFormat()));
+    deckView->expandAll();
+    deckView->expandAll();
+
+    emit deckChanged();
 }
 
 DeckLoader *DeckEditorDeckDockWidget::getDeckLoader()
@@ -724,6 +779,8 @@ void DeckEditorDeckDockWidget::retranslateUi()
     showTagsWidgetCheckBox->setText(tr("Show tags selection menu"));
     commentsLabel->setText(tr("&Comments:"));
     activeGroupCriteriaLabel->setText(tr("Group by:"));
+    formatLabel->setText(tr("Format:"));
+
     hashLabel1->setText(tr("Hash:"));
 
     aIncrement->setText(tr("&Increment number"));
diff --git a/cockatrice/src/interface/widgets/deck_editor/deck_editor_deck_dock_widget.h b/cockatrice/src/interface/widgets/deck_editor/deck_editor_deck_dock_widget.h
index d1f1da300..08aa38e5e 100644
--- a/cockatrice/src/interface/widgets/deck_editor/deck_editor_deck_dock_widget.h
+++ b/cockatrice/src/interface/widgets/deck_editor/deck_editor_deck_dock_widget.h
@@ -69,6 +69,7 @@ public slots:
     void actSwapCard();
     void actRemoveCard();
     void offsetCountAtIndex(const QModelIndex &idx, int offset);
+    void initializeFormats();
     void expandAll();
 
 signals:
@@ -100,6 +101,8 @@ private:
     LineEditUnfocusable *hashLabel;
     QLabel *activeGroupCriteriaLabel;
     QComboBox *activeGroupCriteriaComboBox;
+    QLabel *formatLabel;
+    QComboBox *formatComboBox;
 
     QAction *aRemoveCard, *aIncrement, *aDecrement, *aSwapCard;
 
diff --git a/cockatrice/src/interface/widgets/deck_editor/deck_list_style_proxy.cpp b/cockatrice/src/interface/widgets/deck_editor/deck_list_style_proxy.cpp
index 9c2265dfd..14c5faae7 100644
--- a/cockatrice/src/interface/widgets/deck_editor/deck_list_style_proxy.cpp
+++ b/cockatrice/src/interface/widgets/deck_editor/deck_list_style_proxy.cpp
@@ -23,8 +23,7 @@ QVariant DeckListStyleProxy::data(const QModelIndex &index, int role) const
 
     if (role == Qt::BackgroundRole) {
         if (isCard) {
-            const bool legal =
-                true; // TODO: Not implemented yet. QIdentityProxyModel::data(index, DeckRoles::IsLegalRole).toBool();
+            const bool legal = QIdentityProxyModel::data(index, DeckRoles::IsLegalRole).toBool();
             int base = 255 - (index.row() % 2) * 30;
             return legal ? QBrush(QColor(base, base, base)) : QBrush(QColor(255, base / 3, base / 3));
         } else {
diff --git a/cockatrice/src/interface/widgets/tabs/api/archidekt/tab_archidekt.cpp b/cockatrice/src/interface/widgets/tabs/api/archidekt/tab_archidekt.cpp
index 1376efd47..e6615fa7b 100644
--- a/cockatrice/src/interface/widgets/tabs/api/archidekt/tab_archidekt.cpp
+++ b/cockatrice/src/interface/widgets/tabs/api/archidekt/tab_archidekt.cpp
@@ -214,7 +214,7 @@ TabArchidekt::TabArchidekt(TabSupervisor *_tabSupervisor) : Tab(_tabSupervisor)
     minDeckSizeLogicCombo->addItems({"Exact", "≥", "≤"}); // Exact = unset, ≥ = GTE, ≤ = LTE
     minDeckSizeLogicCombo->setCurrentIndex(1);            // default GTE
 
-    connect(minDeckSizeSpin, QOverload<int>::of(&QSpinBox::valueChanged), this, &TabArchidekt::doSearch);
+    connect(minDeckSizeSpin, qOverload<int>(&QSpinBox::valueChanged), this, &TabArchidekt::doSearch);
     connect(minDeckSizeLogicCombo, &QComboBox::currentTextChanged, this, &TabArchidekt::doSearch);
 
     // Page number
@@ -224,7 +224,7 @@ TabArchidekt::TabArchidekt(TabSupervisor *_tabSupervisor) : Tab(_tabSupervisor)
     pageSpin->setRange(1, 9999);
     pageSpin->setValue(1);
 
-    connect(pageSpin, QOverload<int>::of(&QSpinBox::valueChanged), this, &TabArchidekt::doSearch);
+    connect(pageSpin, qOverload<int>(&QSpinBox::valueChanged), this, &TabArchidekt::doSearch);
 
     // Page display
     currentPageDisplay = new QWidget(container);
diff --git a/cockatrice/src/interface/widgets/visual_database_display/visual_database_display_format_legality_filter_widget.cpp b/cockatrice/src/interface/widgets/visual_database_display/visual_database_display_format_legality_filter_widget.cpp
new file mode 100644
index 000000000..1f1b7b94c
--- /dev/null
+++ b/cockatrice/src/interface/widgets/visual_database_display/visual_database_display_format_legality_filter_widget.cpp
@@ -0,0 +1,205 @@
+#include "visual_database_display_format_legality_filter_widget.h"
+
+#include "../../../filters/filter_tree_model.h"
+
+#include <QPushButton>
+#include <QSpinBox>
+#include <QTimer>
+#include <libcockatrice/card/database/card_database_manager.h>
+#include <libcockatrice/filters/filter_tree.h>
+
+VisualDatabaseDisplayFormatLegalityFilterWidget::VisualDatabaseDisplayFormatLegalityFilterWidget(
+    QWidget *parent,
+    FilterTreeModel *_filterModel)
+    : QWidget(parent), filterModel(_filterModel)
+{
+    allFormatsWithCount = CardDatabaseManager::query()->getAllFormatsWithCount();
+
+    setMaximumHeight(75);
+    setSizePolicy(QSizePolicy::Preferred, QSizePolicy::Minimum);
+
+    layout = new QHBoxLayout(this);
+    setLayout(layout);
+    layout->setContentsMargins(0, 1, 0, 1);
+    layout->setSpacing(1);
+    layout->setAlignment(Qt::AlignTop);
+
+    flowWidget = new FlowWidget(this, Qt::Horizontal, Qt::ScrollBarAlwaysOff, Qt::ScrollBarAsNeeded);
+    layout->addWidget(flowWidget);
+
+    // Create the spinbox
+    spinBox = new QSpinBox(this);
+    spinBox->setMinimum(1);
+    spinBox->setMaximum(getMaxMainTypeCount()); // Set the max value dynamically
+    spinBox->setValue(150);
+    layout->addWidget(spinBox);
+    connect(spinBox, qOverload<int>(&QSpinBox::valueChanged), this,
+            &VisualDatabaseDisplayFormatLegalityFilterWidget::updateFormatButtonsVisibility);
+
+    // Create the toggle button for Exact Match/Includes mode
+    toggleButton = new QPushButton(this);
+    toggleButton->setCheckable(true);
+    layout->addWidget(toggleButton);
+    connect(toggleButton, &QPushButton::toggled, this,
+            &VisualDatabaseDisplayFormatLegalityFilterWidget::updateFilterMode);
+    connect(filterModel, &FilterTreeModel::layoutChanged, this, [this]() {
+        QTimer::singleShot(100, this, &VisualDatabaseDisplayFormatLegalityFilterWidget::syncWithFilterModel);
+    });
+
+    createFormatButtons();   // Populate buttons initially
+    updateFilterMode(false); // Initialize toggle button text
+
+    retranslateUi();
+}
+
+void VisualDatabaseDisplayFormatLegalityFilterWidget::retranslateUi()
+{
+    spinBox->setToolTip(tr("Do not display formats with less than this amount of cards in the database"));
+    toggleButton->setToolTip(tr("Filter mode (AND/OR/NOT conjunctions of filters)"));
+}
+
+void VisualDatabaseDisplayFormatLegalityFilterWidget::createFormatButtons()
+{
+    // Iterate through main types and create buttons
+    for (auto it = allFormatsWithCount.begin(); it != allFormatsWithCount.end(); ++it) {
+        auto *button = new QPushButton(it.key(), flowWidget);
+        button->setCheckable(true);
+        button->setStyleSheet("QPushButton { background-color: lightgray; border: 1px solid gray; padding: 5px; }"
+                              "QPushButton:checked { background-color: green; color: white; }");
+
+        flowWidget->addWidget(button);
+        formatButtons[it.key()] = button;
+
+        // Connect toggle signal
+        connect(button, &QPushButton::toggled, this,
+                [this, mainType = it.key()](bool checked) { handleFormatToggled(mainType, checked); });
+    }
+    updateFormatButtonsVisibility(); // Ensure visibility is updated initially
+}
+
+void VisualDatabaseDisplayFormatLegalityFilterWidget::updateFormatButtonsVisibility()
+{
+    int threshold = spinBox->value(); // Get the current spinbox value
+
+    // Iterate through buttons and hide/disable those below the threshold
+    for (auto it = formatButtons.begin(); it != formatButtons.end(); ++it) {
+        bool visible = allFormatsWithCount[it.key()] >= threshold;
+        it.value()->setVisible(visible);
+        it.value()->setEnabled(visible);
+    }
+}
+
+int VisualDatabaseDisplayFormatLegalityFilterWidget::getMaxMainTypeCount() const
+{
+    int maxCount = 1;
+    for (auto it = allFormatsWithCount.begin(); it != allFormatsWithCount.end(); ++it) {
+        maxCount = qMax(maxCount, it.value());
+    }
+    return maxCount;
+}
+
+void VisualDatabaseDisplayFormatLegalityFilterWidget::handleFormatToggled(const QString &format, bool active)
+{
+    activeFormats[format] = active;
+
+    if (formatButtons.contains(format)) {
+        formatButtons[format]->setChecked(active);
+    }
+
+    updateFormatFilter();
+}
+
+void VisualDatabaseDisplayFormatLegalityFilterWidget::updateFormatFilter()
+{
+    // Clear existing filters related to main type
+    filterModel->blockSignals(true);
+    filterModel->filterTree()->blockSignals(true);
+    filterModel->clearFiltersOfType(CardFilter::Attr::AttrFormat);
+
+    if (exactMatchMode) {
+        // Exact Match: Only selected main types are allowed
+        QSet<QString> selectedTypes;
+        for (const auto &type : activeFormats.keys()) {
+            if (activeFormats[type]) {
+                selectedTypes.insert(type);
+            }
+        }
+
+        if (!selectedTypes.isEmpty()) {
+            // Require all selected types (TypeAnd)
+            for (const auto &type : selectedTypes) {
+                QString typeString = type;
+                filterModel->addFilter(
+                    new CardFilter(typeString, CardFilter::Type::TypeAnd, CardFilter::Attr::AttrFormat));
+            }
+
+            // Exclude any other types (TypeAndNot)
+            for (const auto &type : formatButtons.keys()) {
+                if (!selectedTypes.contains(type)) {
+                    QString typeString = type;
+                    filterModel->addFilter(
+                        new CardFilter(typeString, CardFilter::Type::TypeAndNot, CardFilter::Attr::AttrFormat));
+                }
+            }
+        }
+    } else {
+        // Default Includes Mode (TypeOr) - match any selected main types
+        for (const auto &type : activeFormats.keys()) {
+            if (activeFormats[type]) {
+                QString typeString = type;
+                filterModel->addFilter(
+                    new CardFilter(typeString, CardFilter::Type::TypeAnd, CardFilter::Attr::AttrFormat));
+            }
+        }
+    }
+
+    filterModel->blockSignals(false);
+    filterModel->filterTree()->blockSignals(false);
+
+    emit filterModel->filterTree()->changed();
+    emit filterModel->layoutChanged();
+}
+
+void VisualDatabaseDisplayFormatLegalityFilterWidget::updateFilterMode(bool checked)
+{
+    exactMatchMode = checked;
+    toggleButton->setText(exactMatchMode ? tr("Mode: Exact Match") : tr("Mode: Includes"));
+    updateFormatFilter();
+}
+
+void VisualDatabaseDisplayFormatLegalityFilterWidget::syncWithFilterModel()
+{
+    // Temporarily block signals for each button to prevent toggling while updating button states
+    for (auto it = formatButtons.begin(); it != formatButtons.end(); ++it) {
+        it.value()->blockSignals(true);
+    }
+
+    // Uncheck all buttons
+    for (auto it = formatButtons.begin(); it != formatButtons.end(); ++it) {
+        it.value()->setChecked(false);
+    }
+
+    // Get active filters for main types
+    QSet<QString> activeTypes;
+    for (const auto &filter : filterModel->getFiltersOfType(CardFilter::AttrFormat)) {
+        if (filter->type() == CardFilter::Type::TypeAnd) {
+            activeTypes.insert(filter->term());
+        }
+    }
+
+    // Check the buttons for active types
+    for (const auto &type : activeTypes) {
+        activeFormats[type] = true;
+        if (formatButtons.contains(type)) {
+            formatButtons[type]->setChecked(true);
+        }
+    }
+
+    // Re-enable signal emissions for each button
+    for (auto it = formatButtons.begin(); it != formatButtons.end(); ++it) {
+        it.value()->blockSignals(false);
+    }
+
+    // Update the visibility of buttons
+    updateFormatButtonsVisibility();
+}
diff --git a/cockatrice/src/interface/widgets/visual_database_display/visual_database_display_format_legality_filter_widget.h b/cockatrice/src/interface/widgets/visual_database_display/visual_database_display_format_legality_filter_widget.h
new file mode 100644
index 000000000..a2a00b740
--- /dev/null
+++ b/cockatrice/src/interface/widgets/visual_database_display/visual_database_display_format_legality_filter_widget.h
@@ -0,0 +1,43 @@
+#ifndef COCKATRICE_VISUAL_DATABASE_DISPLAY_FORMAT_LEGALITY_FILTER_WIDGET_H
+#define COCKATRICE_VISUAL_DATABASE_DISPLAY_FORMAT_LEGALITY_FILTER_WIDGET_H
+
+#include "../../../filters/filter_tree_model.h"
+#include "../general/layout_containers/flow_widget.h"
+
+#include <QMap>
+#include <QPushButton>
+#include <QSpinBox>
+#include <QToolButton>
+#include <QVBoxLayout>
+#include <QWidget>
+
+class VisualDatabaseDisplayFormatLegalityFilterWidget : public QWidget
+{
+    Q_OBJECT
+public:
+    explicit VisualDatabaseDisplayFormatLegalityFilterWidget(QWidget *parent, FilterTreeModel *filterModel);
+    void retranslateUi();
+    void createFormatButtons();
+    void updateFormatButtonsVisibility();
+    int getMaxMainTypeCount() const;
+
+    void handleFormatToggled(const QString &format, bool active);
+    void updateFormatFilter();
+    void updateFilterMode(bool checked);
+    void syncWithFilterModel();
+
+private:
+    FilterTreeModel *filterModel;
+    QMap<QString, int> allFormatsWithCount;
+    QSpinBox *spinBox;
+    QHBoxLayout *layout;
+    FlowWidget *flowWidget;
+    QPushButton *toggleButton; // Mode switch button
+
+    QMap<QString, bool> activeFormats;          // Track active filters
+    QMap<QString, QPushButton *> formatButtons; // Store toggle buttons
+
+    bool exactMatchMode = false; // Toggle between "Exact Match" and "Includes"
+};
+
+#endif // COCKATRICE_VISUAL_DATABASE_DISPLAY_FORMAT_LEGALITY_FILTER_WIDGET_H
diff --git a/cockatrice/src/interface/widgets/visual_database_display/visual_database_display_main_type_filter_widget.cpp b/cockatrice/src/interface/widgets/visual_database_display/visual_database_display_main_type_filter_widget.cpp
index 32652c346..368ac8719 100644
--- a/cockatrice/src/interface/widgets/visual_database_display/visual_database_display_main_type_filter_widget.cpp
+++ b/cockatrice/src/interface/widgets/visual_database_display/visual_database_display_main_type_filter_widget.cpp
@@ -33,7 +33,7 @@ VisualDatabaseDisplayMainTypeFilterWidget::VisualDatabaseDisplayMainTypeFilterWi
     spinBox->setMaximum(getMaxMainTypeCount()); // Set the max value dynamically
     spinBox->setValue(150);
     layout->addWidget(spinBox);
-    connect(spinBox, QOverload<int>::of(&QSpinBox::valueChanged), this,
+    connect(spinBox, qOverload<int>(&QSpinBox::valueChanged), this,
             &VisualDatabaseDisplayMainTypeFilterWidget::updateMainTypeButtonsVisibility);
 
     // Create the toggle button for Exact Match/Includes mode
diff --git a/cockatrice/src/interface/widgets/visual_database_display/visual_database_display_set_filter_widget.cpp b/cockatrice/src/interface/widgets/visual_database_display/visual_database_display_set_filter_widget.cpp
index 1ea6e8e67..dee89f06a 100644
--- a/cockatrice/src/interface/widgets/visual_database_display/visual_database_display_set_filter_widget.cpp
+++ b/cockatrice/src/interface/widgets/visual_database_display/visual_database_display_set_filter_widget.cpp
@@ -27,7 +27,7 @@ VisualDatabaseDisplayRecentSetFilterSettingsWidget::VisualDatabaseDisplayRecentS
     filterToMostRecentSetsAmount->setMaximum(100);
     filterToMostRecentSetsAmount->setValue(
         SettingsCache::instance().getVisualDatabaseDisplayFilterToMostRecentSetsAmount());
-    connect(filterToMostRecentSetsAmount, QOverload<int>::of(&QSpinBox::valueChanged), &SettingsCache::instance(),
+    connect(filterToMostRecentSetsAmount, qOverload<int>(&QSpinBox::valueChanged), &SettingsCache::instance(),
             &SettingsCache::setVisualDatabaseDisplayFilterToMostRecentSetsAmount);
 
     layout->addWidget(filterToMostRecentSetsCheckBox);
diff --git a/cockatrice/src/interface/widgets/visual_database_display/visual_database_display_sub_type_filter_widget.cpp b/cockatrice/src/interface/widgets/visual_database_display/visual_database_display_sub_type_filter_widget.cpp
index 7a88b51cf..b34bb65d3 100644
--- a/cockatrice/src/interface/widgets/visual_database_display/visual_database_display_sub_type_filter_widget.cpp
+++ b/cockatrice/src/interface/widgets/visual_database_display/visual_database_display_sub_type_filter_widget.cpp
@@ -26,7 +26,7 @@ VisualDatabaseDisplaySubTypeFilterWidget::VisualDatabaseDisplaySubTypeFilterWidg
     spinBox->setMaximum(getMaxSubTypeCount());
     spinBox->setValue(150);
     layout->addWidget(spinBox);
-    connect(spinBox, QOverload<int>::of(&QSpinBox::valueChanged), this,
+    connect(spinBox, qOverload<int>(&QSpinBox::valueChanged), this,
             &VisualDatabaseDisplaySubTypeFilterWidget::updateSubTypeButtonsVisibility);
 
     // Create search box
diff --git a/cockatrice/src/interface/widgets/visual_database_display/visual_database_display_widget.cpp b/cockatrice/src/interface/widgets/visual_database_display/visual_database_display_widget.cpp
index cc0fc8033..c5eaa171a 100644
--- a/cockatrice/src/interface/widgets/visual_database_display/visual_database_display_widget.cpp
+++ b/cockatrice/src/interface/widgets/visual_database_display/visual_database_display_widget.cpp
@@ -206,6 +206,7 @@ void VisualDatabaseDisplayWidget::initialize()
     saveLoadWidget = new VisualDatabaseDisplayFilterSaveLoadWidget(this, filterModel);
     nameFilterWidget = new VisualDatabaseDisplayNameFilterWidget(this, deckEditor, filterModel);
     mainTypeFilterWidget = new VisualDatabaseDisplayMainTypeFilterWidget(this, filterModel);
+    formatLegalityWidget = new VisualDatabaseDisplayFormatLegalityFilterWidget(this, filterModel);
     subTypeFilterWidget = new VisualDatabaseDisplaySubTypeFilterWidget(this, filterModel);
     setFilterWidget = new VisualDatabaseDisplaySetFilterWidget(this, filterModel);
 
@@ -223,6 +224,7 @@ void VisualDatabaseDisplayWidget::initialize()
     filterContainerLayout->addWidget(quickFilterSubTypeWidget);
     filterContainerLayout->addWidget(quickFilterSetWidget);
     filterContainerLayout->addWidget(mainTypeFilterWidget);
+    filterContainerLayout->addWidget(formatLegalityWidget);
 
     searchLayout->addWidget(colorFilterWidget);
     searchLayout->addWidget(clearFilterWidget);
diff --git a/cockatrice/src/interface/widgets/visual_database_display/visual_database_display_widget.h b/cockatrice/src/interface/widgets/visual_database_display/visual_database_display_widget.h
index 5cab2ca9b..24990f8e5 100644
--- a/cockatrice/src/interface/widgets/visual_database_display/visual_database_display_widget.h
+++ b/cockatrice/src/interface/widgets/visual_database_display/visual_database_display_widget.h
@@ -17,6 +17,7 @@
 #include "../utility/custom_line_edit.h"
 #include "visual_database_display_color_filter_widget.h"
 #include "visual_database_display_filter_save_load_widget.h"
+#include "visual_database_display_format_legality_filter_widget.h"
 #include "visual_database_display_main_type_filter_widget.h"
 #include "visual_database_display_name_filter_widget.h"
 #include "visual_database_display_set_filter_widget.h"
@@ -91,6 +92,7 @@ private:
     SettingsButtonWidget *quickFilterNameWidget;
     VisualDatabaseDisplayNameFilterWidget *nameFilterWidget;
     VisualDatabaseDisplayMainTypeFilterWidget *mainTypeFilterWidget;
+    VisualDatabaseDisplayFormatLegalityFilterWidget *formatLegalityWidget;
     SettingsButtonWidget *quickFilterSubTypeWidget;
     VisualDatabaseDisplaySubTypeFilterWidget *subTypeFilterWidget;
     SettingsButtonWidget *quickFilterSetWidget;
diff --git a/cockatrice/src/interface/widgets/visual_deck_editor/visual_deck_editor_sample_hand_widget.cpp b/cockatrice/src/interface/widgets/visual_deck_editor/visual_deck_editor_sample_hand_widget.cpp
index 341b94a3b..778706f9a 100644
--- a/cockatrice/src/interface/widgets/visual_deck_editor/visual_deck_editor_sample_hand_widget.cpp
+++ b/cockatrice/src/interface/widgets/visual_deck_editor/visual_deck_editor_sample_hand_widget.cpp
@@ -24,9 +24,9 @@ VisualDeckEditorSampleHandWidget::VisualDeckEditorSampleHandWidget(QWidget *pare
     handSizeSpinBox = new QSpinBox(this);
     handSizeSpinBox->setValue(SettingsCache::instance().getVisualDeckEditorSampleHandSize());
     handSizeSpinBox->setMinimum(1);
-    connect(handSizeSpinBox, QOverload<int>::of(&QSpinBox::valueChanged), &SettingsCache::instance(),
+    connect(handSizeSpinBox, qOverload<int>(&QSpinBox::valueChanged), &SettingsCache::instance(),
             &SettingsCache::setVisualDeckEditorSampleHandSize);
-    connect(handSizeSpinBox, QOverload<int>::of(&QSpinBox::valueChanged), this,
+    connect(handSizeSpinBox, qOverload<int>(&QSpinBox::valueChanged), this,
             &VisualDeckEditorSampleHandWidget::updateDisplay);
     resetAndHandSizeLayout->addWidget(handSizeSpinBox);
 
diff --git a/cockatrice/src/interface/widgets/visual_deck_storage/visual_deck_storage_quick_settings_widget.cpp b/cockatrice/src/interface/widgets/visual_deck_storage/visual_deck_storage_quick_settings_widget.cpp
index c1e9bfa6a..a396b8cd3 100644
--- a/cockatrice/src/interface/widgets/visual_deck_storage/visual_deck_storage_quick_settings_widget.cpp
+++ b/cockatrice/src/interface/widgets/visual_deck_storage/visual_deck_storage_quick_settings_widget.cpp
@@ -61,10 +61,10 @@ VisualDeckStorageQuickSettingsWidget::VisualDeckStorageQuickSettingsWidget(QWidg
     unusedColorIdentitiesOpacitySpinBox->setMaximum(100);
     unusedColorIdentitiesOpacitySpinBox->setValue(
         SettingsCache::instance().getVisualDeckStorageUnusedColorIdentitiesOpacity());
-    connect(unusedColorIdentitiesOpacitySpinBox, QOverload<int>::of(&QSpinBox::valueChanged), this,
+    connect(unusedColorIdentitiesOpacitySpinBox, qOverload<int>(&QSpinBox::valueChanged), this,
             &VisualDeckStorageQuickSettingsWidget::unusedColorIdentitiesOpacityChanged);
-    connect(unusedColorIdentitiesOpacitySpinBox, QOverload<int>::of(&QSpinBox::valueChanged),
-            &SettingsCache::instance(), &SettingsCache::setVisualDeckStorageUnusedColorIdentitiesOpacity);
+    connect(unusedColorIdentitiesOpacitySpinBox, qOverload<int>(&QSpinBox::valueChanged), &SettingsCache::instance(),
+            &SettingsCache::setVisualDeckStorageUnusedColorIdentitiesOpacity);
 
     unusedColorIdentitiesOpacityLabel->setBuddy(unusedColorIdentitiesOpacitySpinBox);
 
diff --git a/dbconverter/src/main.h b/dbconverter/src/main.h
index 7a5809b1b..d6e734316 100644
--- a/dbconverter/src/main.h
+++ b/dbconverter/src/main.h
@@ -5,6 +5,10 @@
 #include <libcockatrice/card/database/parser/cockatrice_xml_4.h>
 #include <libcockatrice/interfaces/noop_card_preference_provider.h>
 
+static const QList<AllowedCount> kConstructedCounts = {{4, "legal"}, {0, "banned"}};
+
+static const QList<AllowedCount> kSingletonCounts = {{1, "legal"}, {0, "banned"}};
+
 class CardDatabaseConverter : public CardDatabase
 {
 public:
@@ -23,7 +27,73 @@ public:
     bool saveCardDatabase(const QString &fileName)
     {
         CockatriceXml4Parser parser(new NoopCardPreferenceProvider());
-        return parser.saveToFile(sets, cards, fileName);
+
+        return parser.saveToFile(createDefaultMagicFormats(), sets, cards, fileName);
+    }
+
+    FormatRulesNameMap createDefaultMagicFormats()
+    {
+        // Predefined common exceptions
+        CardCondition superTypeIsBasic;
+        superTypeIsBasic.field = "type";
+        superTypeIsBasic.matchType = "contains";
+        superTypeIsBasic.value = "Basic Land";
+
+        ExceptionRule basicLands;
+        basicLands.conditions.append(superTypeIsBasic);
+
+        CardCondition anyNumberAllowed;
+        anyNumberAllowed.field = "text";
+        anyNumberAllowed.matchType = "contains";
+        anyNumberAllowed.value = "A deck can have any number of";
+
+        ExceptionRule mayContainAnyNumber;
+        mayContainAnyNumber.conditions.append(anyNumberAllowed);
+
+        // Map to store default rules
+        FormatRulesNameMap defaultFormatRulesNameMap;
+
+        // ----------------- Helper lambda to create format -----------------
+        auto makeFormat = [&](const QString &name, int minDeck = 60, int maxDeck = -1, int maxSideboardSize = 15,
+                              const QList<AllowedCount> &allowedCounts = kConstructedCounts) -> FormatRulesPtr {
+            FormatRulesPtr f(new FormatRules);
+            f->formatName = name;
+            f->allowedCounts = allowedCounts;
+            f->minDeckSize = minDeck;
+            f->maxDeckSize = maxDeck;
+            f->maxSideboardSize = maxSideboardSize;
+            f->exceptions.append(basicLands);
+            f->exceptions.append(mayContainAnyNumber);
+            defaultFormatRulesNameMap.insert(name.toLower(), f);
+            return f;
+        };
+
+        // ----------------- Standard formats -----------------
+        makeFormat("Standard");
+        makeFormat("Modern");
+        makeFormat("Legacy");
+        makeFormat("Pioneer");
+        makeFormat("Historic");
+        makeFormat("Timeless");
+        makeFormat("Future");
+        makeFormat("OldSchool");
+        makeFormat("Premodern");
+        makeFormat("Pauper");
+        makeFormat("Penny");
+
+        // ----------------- Singleton formats -----------------
+        makeFormat("Commander", 100, 100, 15, kSingletonCounts);
+        makeFormat("Duel", 100, 100, 15, kSingletonCounts);
+        makeFormat("Brawl", 60, 60, 15, kSingletonCounts);
+        makeFormat("StandardBrawl", 60, 60, 15, kSingletonCounts);
+        makeFormat("Oathbreaker", 60, 60, 15, kSingletonCounts);
+        makeFormat("PauperCommander", 100, 100, 15, kSingletonCounts);
+        makeFormat("Predh", 100, 100, 15, kSingletonCounts);
+
+        // ----------------- Restricted formats -----------------
+        makeFormat("Vintage", 60, -1, 15, {{4, "legal"}, {1, "restricted"}, {0, "banned"}});
+
+        return defaultFormatRulesNameMap;
     }
 };
 
diff --git a/libcockatrice_card/CMakeLists.txt b/libcockatrice_card/CMakeLists.txt
index 857376163..f516cde00 100644
--- a/libcockatrice_card/CMakeLists.txt
+++ b/libcockatrice_card/CMakeLists.txt
@@ -41,6 +41,8 @@ add_library(
   libcockatrice/card/relation/card_relation.cpp
   libcockatrice/card/set/card_set.cpp
   libcockatrice/card/set/card_set_list.cpp
+  libcockatrice/card/format/format_legality_rules.cpp
+  libcockatrice/card/format/format_legality_rules.h
 )
 
 target_include_directories(
diff --git a/libcockatrice_card/libcockatrice/card/card_info.h b/libcockatrice_card/libcockatrice/card/card_info.h
index 7bd51356c..00e8fec37 100644
--- a/libcockatrice_card/libcockatrice/card/card_info.h
+++ b/libcockatrice_card/libcockatrice/card/card_info.h
@@ -1,6 +1,7 @@
 #ifndef CARD_INFO_H
 #define CARD_INFO_H
 
+#include "format/format_legality_rules.h"
 #include "printing/printing_info.h"
 
 #include <QDate>
@@ -22,10 +23,12 @@ class ICardDatabaseParser;
 
 typedef QSharedPointer<CardInfo> CardInfoPtr;
 typedef QSharedPointer<CardSet> CardSetPtr;
+typedef QSharedPointer<FormatRules> FormatRulesPtr;
 typedef QMap<QString, QList<PrintingInfo>> SetToPrintingsMap;
 
 typedef QHash<QString, CardInfoPtr> CardNameMap;
 typedef QHash<QString, CardSetPtr> SetNameMap;
+typedef QHash<QString, FormatRulesPtr> FormatRulesNameMap;
 
 Q_DECLARE_METATYPE(CardInfoPtr)
 
diff --git a/libcockatrice_card/libcockatrice/card/database/card_database.cpp b/libcockatrice_card/libcockatrice/card/database/card_database.cpp
index 2e977901f..de84ad814 100644
--- a/libcockatrice_card/libcockatrice/card/database/card_database.cpp
+++ b/libcockatrice_card/libcockatrice/card/database/card_database.cpp
@@ -199,3 +199,8 @@ void CardDatabase::notifyEnabledSetsChanged()
     // inform the carddatabasemodels that they need to re-check their list of cards
     emit cardDatabaseEnabledSetsChanged();
 }
+
+void CardDatabase::addFormat(FormatRulesPtr format)
+{
+    formats.insert(format->formatName.toLower(), format);
+}
\ No newline at end of file
diff --git a/libcockatrice_card/libcockatrice/card/database/card_database.h b/libcockatrice_card/libcockatrice/card/database/card_database.h
index 6028cce86..7f8fc39db 100644
--- a/libcockatrice_card/libcockatrice/card/database/card_database.h
+++ b/libcockatrice_card/libcockatrice/card/database/card_database.h
@@ -42,6 +42,8 @@ protected:
     /// Sets indexed by short name
     SetNameMap sets;
 
+    FormatRulesNameMap formats;
+
     /// Loader responsible for file discovery and parsing
     CardDatabaseLoader *loader;
 
@@ -141,6 +143,8 @@ public slots:
      */
     void addSet(CardSetPtr set);
 
+    void addFormat(FormatRulesPtr format);
+
     /** @brief Loads card databases from configured paths. */
     void loadCardDatabases();
 
diff --git a/libcockatrice_card/libcockatrice/card/database/card_database_loader.cpp b/libcockatrice_card/libcockatrice/card/database/card_database_loader.cpp
index f56f6a0b5..91bb4c741 100644
--- a/libcockatrice_card/libcockatrice/card/database/card_database_loader.cpp
+++ b/libcockatrice_card/libcockatrice/card/database/card_database_loader.cpp
@@ -23,6 +23,7 @@ CardDatabaseLoader::CardDatabaseLoader(QObject *parent,
         // connect parser outputs to the database adders
         connect(p, &ICardDatabaseParser::addCard, database, &CardDatabase::addCard, Qt::DirectConnection);
         connect(p, &ICardDatabaseParser::addSet, database, &CardDatabase::addSet, Qt::DirectConnection);
+        connect(p, &ICardDatabaseParser::addFormat, database, &CardDatabase::addFormat, Qt::DirectConnection);
     }
 
     // when SettingsCache's path changes, trigger reloads
@@ -149,6 +150,6 @@ bool CardDatabaseLoader::saveCustomTokensToFile()
         }
     }
 
-    availableParsers.first()->saveToFile(tmpSets, tmpCards, fileName);
+    availableParsers.first()->saveToFile(FormatRulesNameMap(), tmpSets, tmpCards, fileName);
     return true;
 }
diff --git a/libcockatrice_card/libcockatrice/card/database/card_database_querier.cpp b/libcockatrice_card/libcockatrice/card/database/card_database_querier.cpp
index 65999e590..b2a675b99 100644
--- a/libcockatrice_card/libcockatrice/card/database/card_database_querier.cpp
+++ b/libcockatrice_card/libcockatrice/card/database/card_database_querier.cpp
@@ -341,4 +341,27 @@ QMap<QString, int> CardDatabaseQuerier::getAllSubCardTypesWithCount() const
     }
 
     return typeCounts;
+}
+
+FormatRulesPtr CardDatabaseQuerier::getFormat(const QString &formatName) const
+{
+    return db->formats.value(formatName.toLower());
+}
+
+QMap<QString, int> CardDatabaseQuerier::getAllFormatsWithCount() const
+{
+    QMap<QString, int> formatCounts;
+
+    for (const auto &card : db->cards.values()) {
+        QStringList allProps = card->getProperties();
+
+        for (const QString &prop : allProps) {
+            if (prop.startsWith("format-")) {
+                QString formatName = prop.mid(QStringLiteral("format-").size());
+                formatCounts[formatName]++;
+            }
+        }
+    }
+
+    return formatCounts;
 }
\ No newline at end of file
diff --git a/libcockatrice_card/libcockatrice/card/database/card_database_querier.h b/libcockatrice_card/libcockatrice/card/database/card_database_querier.h
index d9a980f06..ff8d7958b 100644
--- a/libcockatrice_card/libcockatrice/card/database/card_database_querier.h
+++ b/libcockatrice_card/libcockatrice/card/database/card_database_querier.h
@@ -214,6 +214,8 @@ public:
      * @return Map of subtype string to count.
      */
     [[nodiscard]] QMap<QString, int> getAllSubCardTypesWithCount() const;
+    FormatRulesPtr getFormat(const QString &formatName) const;
+    QMap<QString, int> getAllFormatsWithCount() const;
 
 private:
     const CardDatabase *db;               //!< Card database used for all lookups.
diff --git a/libcockatrice_card/libcockatrice/card/database/parser/card_database_parser.h b/libcockatrice_card/libcockatrice/card/database/parser/card_database_parser.h
index 35012dbc5..93d46a3cc 100644
--- a/libcockatrice_card/libcockatrice/card/database/parser/card_database_parser.h
+++ b/libcockatrice_card/libcockatrice/card/database/parser/card_database_parser.h
@@ -38,6 +38,7 @@ public:
 
     /**
      * @brief Saves card and set data to a file.
+     * @param _formats
      * @param sets Map of sets to save.
      * @param cards Map of cards to save.
      * @param fileName Target file path.
@@ -45,7 +46,8 @@ public:
      * @param sourceVersion Optional version string of the source.
      * @return true if save succeeded.
      */
-    virtual bool saveToFile(SetNameMap sets,
+    virtual bool saveToFile(FormatRulesNameMap _formats,
+                            SetNameMap sets,
                             CardNameMap cards,
                             const QString &fileName,
                             const QString &sourceUrl = "unknown",
@@ -79,6 +81,8 @@ signals:
 
     /** Emitted when a set is loaded from the database. */
     void addSet(CardSetPtr set);
+
+    void addFormat(FormatRulesPtr format);
 };
 
 Q_DECLARE_INTERFACE(ICardDatabaseParser, "ICardDatabaseParser")
diff --git a/libcockatrice_card/libcockatrice/card/database/parser/cockatrice_xml_3.cpp b/libcockatrice_card/libcockatrice/card/database/parser/cockatrice_xml_3.cpp
index 35e2f3d83..9df396c74 100644
--- a/libcockatrice_card/libcockatrice/card/database/parser/cockatrice_xml_3.cpp
+++ b/libcockatrice_card/libcockatrice/card/database/parser/cockatrice_xml_3.cpp
@@ -438,12 +438,15 @@ static QXmlStreamWriter &operator<<(QXmlStreamWriter &xml, const CardInfoPtr &in
     return xml;
 }
 
-bool CockatriceXml3Parser::saveToFile(SetNameMap _sets,
+bool CockatriceXml3Parser::saveToFile(FormatRulesNameMap _formats,
+                                      SetNameMap _sets,
                                       CardNameMap cards,
                                       const QString &fileName,
                                       const QString &sourceUrl,
                                       const QString &sourceVersion)
 {
+    Q_UNUSED(_formats);
+
     QFile file(fileName);
     if (!file.open(QIODevice::WriteOnly)) {
         return false;
diff --git a/libcockatrice_card/libcockatrice/card/database/parser/cockatrice_xml_3.h b/libcockatrice_card/libcockatrice/card/database/parser/cockatrice_xml_3.h
index a727561ea..c3a261739 100644
--- a/libcockatrice_card/libcockatrice/card/database/parser/cockatrice_xml_3.h
+++ b/libcockatrice_card/libcockatrice/card/database/parser/cockatrice_xml_3.h
@@ -46,7 +46,8 @@ public:
     /**
      * @brief Save sets and cards back to an XML3 file.
      */
-    bool saveToFile(SetNameMap _sets,
+    bool saveToFile(FormatRulesNameMap _formats,
+                    SetNameMap _sets,
                     CardNameMap cards,
                     const QString &fileName,
                     const QString &sourceUrl = "unknown",
diff --git a/libcockatrice_card/libcockatrice/card/database/parser/cockatrice_xml_4.cpp b/libcockatrice_card/libcockatrice/card/database/parser/cockatrice_xml_4.cpp
index ab4c8002d..0d46aad0f 100644
--- a/libcockatrice_card/libcockatrice/card/database/parser/cockatrice_xml_4.cpp
+++ b/libcockatrice_card/libcockatrice/card/database/parser/cockatrice_xml_4.cpp
@@ -6,6 +6,7 @@
 #include <QDebug>
 #include <QFile>
 #include <QXmlStreamReader>
+#include <libcockatrice/card/format/format_legality_rules.h>
 #include <version_string.h>
 
 #define COCKATRICE_XML4_TAGNAME "cockatrice_carddatabase"
@@ -60,7 +61,9 @@ void CockatriceXml4Parser::parseFile(QIODevice &device)
                 }
 
                 auto xmlName = xml.name().toString();
-                if (xmlName == "sets") {
+                if (xmlName == "formats") {
+                    loadFormats(xml);
+                } else if (xmlName == "sets") {
                     loadSetsFromXml(xml);
                 } else if (xmlName == "cards") {
                     loadCardsFromXml(xml);
@@ -78,6 +81,116 @@ void CockatriceXml4Parser::parseFile(QIODevice &device)
     }
 }
 
+static QSharedPointer<FormatRules> parseFormat(QXmlStreamReader &xml)
+{
+    auto rulesPtr = FormatRulesPtr(new FormatRules());
+
+    if (xml.attributes().hasAttribute("formatName")) {
+        rulesPtr->formatName = xml.attributes().value("formatName").toString();
+    }
+
+    while (!xml.atEnd()) {
+        auto token = xml.readNext();
+
+        if (token == QXmlStreamReader::EndElement && xml.name().toString() == "format") {
+            break;
+        }
+
+        if (token != QXmlStreamReader::StartElement) {
+            continue;
+        }
+
+        QString xmlName = xml.name().toString();
+
+        if (xmlName == "minDeckSize") {
+            rulesPtr->minDeckSize = xml.readElementText().toInt();
+        } else if (xmlName == "maxDeckSize") {
+            QString text = xml.readElementText();
+            rulesPtr->maxDeckSize = text.toInt();
+        } else if (xmlName == "maxSideboardSize") {
+            rulesPtr->maxSideboardSize = xml.readElementText().toInt();
+        } else if (xmlName == "allowedCounts") {
+            while (!xml.atEnd()) {
+                token = xml.readNext();
+
+                if (token == QXmlStreamReader::EndElement && xml.name().toString() == "allowedCounts") {
+                    break;
+                }
+
+                if (token == QXmlStreamReader::StartElement && xml.name().toString() == "count") {
+
+                    AllowedCount c;
+
+                    QString maxAttr = xml.attributes().value("max").toString();
+                    c.max = (maxAttr == "unlimited") ? -1 : maxAttr.toInt();
+
+                    c.label = xml.readElementText().trimmed();
+
+                    rulesPtr->allowedCounts.append(c);
+                }
+            }
+        } else if (xmlName == "exceptions") {
+            while (!xml.atEnd()) {
+                token = xml.readNext();
+
+                if (token == QXmlStreamReader::EndElement && xml.name().toString() == "exceptions") {
+                    break;
+                }
+
+                if (token == QXmlStreamReader::StartElement && xml.name().toString() == "exception") {
+                    ExceptionRule ex;
+
+                    while (!xml.atEnd()) {
+                        token = xml.readNext();
+
+                        if (token == QXmlStreamReader::EndElement && xml.name().toString() == "exception") {
+                            break;
+                        }
+
+                        if (token == QXmlStreamReader::StartElement) {
+                            QString ename = xml.name().toString();
+
+                            if (ename == "maxCopies") {
+                                QString text = xml.readElementText();
+                                ex.maxCopies = (text == "unlimited") ? -1 : text.toInt();
+                            } else if (ename == "cardCondition") {
+                                CardCondition cond;
+                                cond.field = xml.attributes().value("field").toString();
+                                cond.matchType = xml.attributes().value("match").toString();
+                                cond.value = xml.attributes().value("value").toString();
+                                ex.conditions.append(cond);
+                                xml.skipCurrentElement();
+                            } else {
+                                xml.skipCurrentElement();
+                            }
+                        }
+                    }
+
+                    rulesPtr->exceptions.append(ex);
+                }
+            }
+        } else {
+            xml.skipCurrentElement();
+        }
+    }
+
+    return rulesPtr;
+}
+
+void CockatriceXml4Parser::loadFormats(QXmlStreamReader &xml)
+{
+    while (!xml.atEnd()) {
+        if (xml.readNext() == QXmlStreamReader::EndElement) {
+            break;
+        }
+
+        if (xml.name().toString() == "format") {
+            auto rulesPtr = parseFormat(xml);
+            emit addFormat(rulesPtr);
+        }
+    }
+}
+
 void CockatriceXml4Parser::loadSetsFromXml(QXmlStreamReader &xml)
 {
     while (!xml.atEnd()) {
@@ -273,6 +386,59 @@ void CockatriceXml4Parser::loadCardsFromXml(QXmlStreamReader &xml)
     }
 }
 
+static QXmlStreamWriter &operator<<(QXmlStreamWriter &xml, const QSharedPointer<FormatRules> &rulesPtr)
+{
+    if (rulesPtr.isNull()) {
+        qCWarning(CockatriceXml4Log) << "&operator<< FormatRules is nullptr";
+        return xml;
+    }
+
+    const FormatRules &rules = *rulesPtr;
+
+    xml.writeStartElement("format");
+    if (!rules.formatName.isEmpty()) {
+        xml.writeAttribute("formatName", rules.formatName);
+    }
+
+    xml.writeTextElement("minDeckSize", QString::number(rules.minDeckSize));
+    xml.writeTextElement("maxDeckSize", rules.maxDeckSize >= 0 ? QString::number(rules.maxDeckSize) : "0");
+    xml.writeTextElement("maxSideboardSize", QString::number(rules.maxSideboardSize));
+    if (!rules.allowedCounts.isEmpty()) {
+        xml.writeStartElement("allowedCounts");
+
+        for (const AllowedCount &c : rules.allowedCounts) {
+            xml.writeStartElement("count");
+            xml.writeAttribute("max", c.max == -1 ? "unlimited" : QString::number(c.max));
+            xml.writeCharacters(c.label);
+            xml.writeEndElement(); // count
+        }
+
+        xml.writeEndElement(); // allowedCounts
+    }
+
+    if (!rules.exceptions.isEmpty()) {
+        xml.writeStartElement("exceptions");
+        for (const ExceptionRule &ex : rules.exceptions) {
+            xml.writeStartElement("exception");
+            xml.writeTextElement("maxCopies", ex.maxCopies == -1 ? "unlimited" : QString::number(ex.maxCopies));
+
+            for (const CardCondition &cond : ex.conditions) {
+                xml.writeStartElement("cardCondition");
+                xml.writeAttribute("field", cond.field);
+                xml.writeAttribute("match", cond.matchType);
+                xml.writeAttribute("value", cond.value);
+                xml.writeEndElement(); // cardCondition
+            }
+
+            xml.writeEndElement(); // exception
+        }
+        xml.writeEndElement(); // exceptions
+    }
+
+    xml.writeEndElement(); // format
+    return xml;
+}
+
 static QXmlStreamWriter &operator<<(QXmlStreamWriter &xml, const CardSetPtr &set)
 {
     if (set.isNull()) {
@@ -399,7 +565,8 @@ static QXmlStreamWriter &operator<<(QXmlStreamWriter &xml, const CardInfoPtr &in
     return xml;
 }
 
-bool CockatriceXml4Parser::saveToFile(SetNameMap _sets,
+bool CockatriceXml4Parser::saveToFile(FormatRulesNameMap _formats,
+                                      SetNameMap _sets,
                                       CardNameMap cards,
                                       const QString &fileName,
                                       const QString &sourceUrl,
@@ -426,6 +593,14 @@ bool CockatriceXml4Parser::saveToFile(SetNameMap _sets,
     xml.writeTextElement("sourceVersion", sourceVersion);
     xml.writeEndElement();
 
+    if (_formats.count() > 0) {
+        xml.writeStartElement("formats");
+        for (FormatRulesPtr format : _formats) {
+            xml << format;
+        }
+        xml.writeEndElement();
+    }
+
     if (_sets.count() > 0) {
         xml.writeStartElement("sets");
         for (CardSetPtr set : _sets) {
diff --git a/libcockatrice_card/libcockatrice/card/database/parser/cockatrice_xml_4.h b/libcockatrice_card/libcockatrice/card/database/parser/cockatrice_xml_4.h
index b83f6929e..5b47e9090 100644
--- a/libcockatrice_card/libcockatrice/card/database/parser/cockatrice_xml_4.h
+++ b/libcockatrice_card/libcockatrice/card/database/parser/cockatrice_xml_4.h
@@ -49,7 +49,8 @@ public:
     /**
      * @brief Save sets and cards back to an XML4 file.
      */
-    bool saveToFile(SetNameMap _sets,
+    bool saveToFile(FormatRulesNameMap _formats,
+                    SetNameMap _sets,
                     CardNameMap cards,
                     const QString &fileName,
                     const QString &sourceUrl = "unknown",
@@ -72,6 +73,7 @@ private:
      */
     void loadCardsFromXml(QXmlStreamReader &xml);
 
+    void loadFormats(QXmlStreamReader &xml);
     /**
      * @brief Load all <set> elements from the XML stream.
      * @param xml The open QXmlStreamReader positioned at the <sets> element.
diff --git a/libcockatrice_card/libcockatrice/card/format/format_legality_rules.cpp b/libcockatrice_card/libcockatrice/card/format/format_legality_rules.cpp
new file mode 100644
index 000000000..a6b3bb038
--- /dev/null
+++ b/libcockatrice_card/libcockatrice/card/format/format_legality_rules.cpp
@@ -0,0 +1,53 @@
+#include "format_legality_rules.h"
+
+#include <libcockatrice/card/card_info.h>
+
+bool cardMatchesCondition(const CardInfo &card, const CardCondition &cond)
+{
+    CardMatchType type = matchTypeFromString(cond.matchType);
+    QString fieldValue;
+    if (cond.field == "name") {
+        fieldValue = card.getName();
+    } else if (cond.field == "text") {
+        fieldValue = card.getText();
+    } else {
+        fieldValue = card.getProperty(cond.field);
+    }
+
+    switch (type) {
+        case CardMatchType::Equals:
+            return fieldValue == cond.value;
+        case CardMatchType::NotEquals:
+            return fieldValue != cond.value;
+        case CardMatchType::Contains:
+            return fieldValue.contains(cond.value, Qt::CaseInsensitive);
+        case CardMatchType::NotContains:
+            return !fieldValue.contains(cond.value, Qt::CaseInsensitive);
+        case CardMatchType::Regex: {
+            QRegularExpression re(cond.value, QRegularExpression::CaseInsensitiveOption);
+            return re.match(fieldValue).hasMatch();
+        }
+        default:
+            return false;
+    }
+}
+
+bool exceptionAppliesToCard(const CardInfo &card, const ExceptionRule &rule)
+{
+    for (const CardCondition &cond : rule.conditions) {
+        if (!cardMatchesCondition(card, cond)) {
+            return false; // all conditions must match
+        }
+    }
+    return true;
+}
+
+bool cardHasAnyException(const CardInfo &card, const FormatRules &format)
+{
+    for (const ExceptionRule &rule : format.exceptions) {
+        if (exceptionAppliesToCard(card, rule)) {
+            return true;
+        }
+    }
+    return false;
+}
\ No newline at end of file
diff --git a/libcockatrice_card/libcockatrice/card/format/format_legality_rules.h b/libcockatrice_card/libcockatrice/card/format/format_legality_rules.h
new file mode 100644
index 000000000..16f2359ab
--- /dev/null
+++ b/libcockatrice_card/libcockatrice/card/format/format_legality_rules.h
@@ -0,0 +1,73 @@
+#ifndef COCKATRICE_FORMAT_LEGALITY_RULES_H
+#define COCKATRICE_FORMAT_LEGALITY_RULES_H
+
+#include <QRegularExpression>
+#include <QSharedPointer>
+#include <QString>
+
+class CardInfo;
+using CardInfoPtr = QSharedPointer<CardInfo>;
+
+struct CardCondition
+{
+    QString field;     // e.g. "type", "maintype", "text"
+    QString matchType; // "contains", "equals", "regex", "notContains", etc.
+    QString value;     // e.g. "Basic Land"
+};
+
+struct AllowedCount
+{
+    int max = 0;   // 4, 1, 0, or -1 for unlimited
+    QString label; // "legal", "restricted", "banned"
+};
+
+struct ExceptionRule
+{
+    QList<CardCondition> conditions; // All must match
+    int maxCopies = -1;              // -1 = unlimited
+};
+
+struct FormatRules
+{
+    QString formatName;
+    int minDeckSize = 60;
+    int maxDeckSize = -1; // -1 = unlimited
+    int maxSideboardSize = 15;
+
+    QList<AllowedCount> allowedCounts;
+
+    QList<ExceptionRule> exceptions; // Cards allowed to break maxCopies
+};
+
+enum class CardMatchType
+{
+    Equals,
+    NotEquals,
+    Contains,
+    NotContains,
+    Regex
+};
+
+// convert string to enum
+inline CardMatchType matchTypeFromString(const QString &str)
+{
+    if (str == "equals")
+        return CardMatchType::Equals;
+    if (str == "notEquals")
+        return CardMatchType::NotEquals;
+    if (str == "contains")
+        return CardMatchType::Contains;
+    if (str == "notContains")
+        return CardMatchType::NotContains;
+    if (str == "regex")
+        return CardMatchType::Regex;
+    return CardMatchType::Equals; // fallback default
+}
+
+bool cardMatchesCondition(const CardInfo &card, const CardCondition &cond);
+
+bool exceptionAppliesToCard(const CardInfo &card, const ExceptionRule &rule);
+
+bool cardHasAnyException(const CardInfo &card, const FormatRules &format);
+
+#endif // COCKATRICE_FORMAT_LEGALITY_RULES_H
diff --git a/libcockatrice_deck_list/libcockatrice/deck_list/deck_list.cpp b/libcockatrice_deck_list/libcockatrice/deck_list/deck_list.cpp
index 333be017b..09326e619 100644
--- a/libcockatrice_deck_list/libcockatrice/deck_list/deck_list.cpp
+++ b/libcockatrice_deck_list/libcockatrice/deck_list/deck_list.cpp
@@ -136,6 +136,8 @@ bool DeckList::readElement(QXmlStreamReader *xml)
             metadata.lastLoadedTimestamp = xml->readElementText();
         } else if (childName == "deckname") {
             metadata.name = xml->readElementText();
+        } else if (childName == "format") {
+            metadata.gameFormat = xml->readElementText();
         } else if (childName == "comments") {
             metadata.comments = xml->readElementText();
         } else if (childName == "bannerCard") {
@@ -170,6 +172,7 @@ void writeMetadata(QXmlStreamWriter *xml, const DeckList::Metadata &metadata)
 {
     xml->writeTextElement("lastLoadedTimestamp", metadata.lastLoadedTimestamp);
     xml->writeTextElement("deckname", metadata.name);
+    xml->writeTextElement("format", metadata.gameFormat);
     xml->writeStartElement("bannerCard");
     xml->writeAttribute("providerId", metadata.bannerCard.providerId);
     xml->writeCharacters(metadata.bannerCard.name);
@@ -594,15 +597,16 @@ DecklistCardNode *DeckList::addCard(const QString &cardName,
                                     const int position,
                                     const QString &cardSetName,
                                     const QString &cardSetCollectorNumber,
-                                    const QString &cardProviderId)
+                                    const QString &cardProviderId,
+                                    const bool formatLegal)
 {
     auto *zoneNode = dynamic_cast<InnerDecklistNode *>(root->findChild(zoneName));
     if (zoneNode == nullptr) {
         zoneNode = new InnerDecklistNode(zoneName, root);
     }
 
-    auto *node =
-        new DecklistCardNode(cardName, 1, zoneNode, position, cardSetName, cardSetCollectorNumber, cardProviderId);
+    auto *node = new DecklistCardNode(cardName, 1, zoneNode, position, cardSetName, cardSetCollectorNumber,
+                                      cardProviderId, formatLegal);
     refreshDeckHash();
 
     return node;
diff --git a/libcockatrice_deck_list/libcockatrice/deck_list/deck_list.h b/libcockatrice_deck_list/libcockatrice/deck_list/deck_list.h
index 6f90b6b14..e4206ebc6 100644
--- a/libcockatrice_deck_list/libcockatrice/deck_list/deck_list.h
+++ b/libcockatrice_deck_list/libcockatrice/deck_list/deck_list.h
@@ -126,6 +126,7 @@ public:
     {
         QString name;                ///< User-defined deck name.
         QString comments;            ///< Free-form comments or notes.
+        QString gameFormat;          ///< The name of the game format this deck contains legal cards for
         CardRef bannerCard;          ///< Optional representative card for the deck.
         QStringList tags;            ///< User-defined tags for deck classification.
         QString lastLoadedTimestamp; ///< Timestamp string of last load.
@@ -181,6 +182,10 @@ public:
     {
         metadata.lastLoadedTimestamp = _lastLoadedTimestamp;
     }
+    void setGameFormat(const QString &_gameFormat = QString())
+    {
+        metadata.gameFormat = _gameFormat;
+    }
     ///@}
 
     /// @brief Construct an empty deck.
@@ -219,6 +224,10 @@ public:
     {
         return metadata.lastLoadedTimestamp;
     }
+    QString getGameFormat() const
+    {
+        return metadata.gameFormat;
+    }
     ///@}
 
     bool isBlankDeck() const
@@ -277,7 +286,8 @@ public:
                               int position,
                               const QString &cardSetName = QString(),
                               const QString &cardSetCollectorNumber = QString(),
-                              const QString &cardProviderId = QString());
+                              const QString &cardProviderId = QString(),
+                              const bool formatLegal = true);
     bool deleteNode(AbstractDecklistNode *node, InnerDecklistNode *rootNode = nullptr);
     ///@}
 
diff --git a/libcockatrice_deck_list/libcockatrice/deck_list/tree/abstract_deck_list_card_node.h b/libcockatrice_deck_list/libcockatrice/deck_list/tree/abstract_deck_list_card_node.h
index 1d201a4c1..88d8b0930 100644
--- a/libcockatrice_deck_list/libcockatrice/deck_list/tree/abstract_deck_list_card_node.h
+++ b/libcockatrice_deck_list/libcockatrice/deck_list/tree/abstract_deck_list_card_node.h
@@ -88,6 +88,12 @@ public:
     /// @param _cardSetNumber Set the collector number.
     virtual void setCardCollectorNumber(const QString &_cardSetNumber) = 0;
 
+    /// @return The format legality of the card
+    virtual bool getFormatLegality() const = 0;
+
+    /// @param _formatLegal If the card is considered legal
+    virtual void setFormatLegality(const bool _formatLegal) = 0;
+
     /**
      * @brief Get the height of this node in the tree.
      *
diff --git a/libcockatrice_deck_list/libcockatrice/deck_list/tree/deck_list_card_node.h b/libcockatrice_deck_list/libcockatrice/deck_list/tree/deck_list_card_node.h
index c2fe038e6..b3d42b89a 100644
--- a/libcockatrice_deck_list/libcockatrice/deck_list/tree/deck_list_card_node.h
+++ b/libcockatrice_deck_list/libcockatrice/deck_list/tree/deck_list_card_node.h
@@ -51,6 +51,7 @@ class DecklistCardNode : public AbstractDecklistCardNode
     QString cardSetShortName; ///< Short set code (e.g., "NEO").
     QString cardSetNumber;    ///< Collector number within the set.
     QString cardProviderId;   ///< External provider identifier (e.g., UUID).
+    bool formatLegal;         ///< Format legality
 
 public:
     /**
@@ -63,6 +64,7 @@ public:
      * @param _cardSetShortName Short set code (e.g., "NEO").
      * @param _cardSetNumber Collector number within the set.
      * @param _cardProviderId External provider ID (e.g., UUID).
+     * @param _formatLegality If the card is legal in the format
      *
      * On construction, if a parent is provided, this node is inserted into
      * the parent’s children list automatically.
@@ -73,10 +75,11 @@ public:
                               int position = -1,
                               QString _cardSetShortName = QString(),
                               QString _cardSetNumber = QString(),
-                              QString _cardProviderId = QString())
+                              QString _cardProviderId = QString(),
+                              bool _formatLegality = true)
         : AbstractDecklistCardNode(_parent, position), name(std::move(_name)), number(_number),
           cardSetShortName(std::move(_cardSetShortName)), cardSetNumber(std::move(_cardSetNumber)),
-          cardProviderId(std::move(_cardProviderId))
+          cardProviderId(std::move(_cardProviderId)), formatLegal(_formatLegality)
     {
     }
 
@@ -150,6 +153,18 @@ public:
         cardSetNumber = _cardSetNumber;
     }
 
+    /// @return The format legality of the card
+    [[nodiscard]] bool getFormatLegality() const override
+    {
+        return formatLegal;
+    }
+
+    /// @param _formatLegal If the card is considered legal
+    void setFormatLegality(const bool _formatLegal) override
+    {
+        formatLegal = _formatLegal;
+    }
+
     /// @return Always false; card nodes are not deck headers.
     [[nodiscard]] bool isDeckHeader() const override
     {
diff --git a/libcockatrice_models/libcockatrice/models/deck_list/deck_list_model.cpp b/libcockatrice_models/libcockatrice/models/deck_list/deck_list_model.cpp
index 2856198b8..05ee480a5 100644
--- a/libcockatrice_models/libcockatrice/models/deck_list/deck_list_model.cpp
+++ b/libcockatrice_models/libcockatrice/models/deck_list/deck_list_model.cpp
@@ -168,6 +168,10 @@ QVariant DeckListModel::data(const QModelIndex &index, int role) const
             return card->depth();
         }
 
+        case DeckRoles::IsLegalRole: {
+            return card->getFormatLegality();
+        }
+
         default: {
             return {};
         }
@@ -268,6 +272,7 @@ bool DeckListModel::setData(const QModelIndex &index, const QVariant &value, con
     switch (index.column()) {
         case DeckListModelColumns::CARD_AMOUNT:
             node->setNumber(value.toInt());
+            refreshCardFormatLegalities();
             break;
         case DeckListModelColumns::CARD_NAME:
             node->setName(value.toString());
@@ -414,8 +419,9 @@ QModelIndex DeckListModel::addCard(const ExactCard &card, const QString &zoneNam
         // Determine the correct index
         int insertRow = findSortedInsertRow(groupNode, cardInfo);
 
-        auto *decklistCard = deckList->addCard(cardInfo->getName(), zoneName, insertRow, cardSetName,
-                                               printingInfo.getProperty("num"), printingInfo.getProperty("uuid"));
+        auto *decklistCard =
+            deckList->addCard(cardInfo->getName(), zoneName, insertRow, cardSetName, printingInfo.getProperty("num"),
+                              printingInfo.getProperty("uuid"), isCardLegalForCurrentFormat(cardInfo));
 
         beginInsertRows(parentIndex, insertRow, insertRow);
         cardNode = new DecklistModelCardNode(decklistCard, groupNode, insertRow);
@@ -532,6 +538,13 @@ void DeckListModel::setActiveGroupCriteria(DeckListModelGroupCriteria::Type newC
     rebuildTree();
 }
 
+void DeckListModel::setActiveFormat(const QString &_format)
+{
+    deckList->setGameFormat(_format);
+    refreshCardFormatLegalities();
+    emitBackgroundUpdates(QModelIndex()); // start from root
+}
+
 void DeckListModel::cleanList()
 {
     setDeckList(new DeckList);
@@ -595,4 +608,90 @@ QList<QString> DeckListModel::getZones() const
                    [](auto zoneNode) { return zoneNode->getName(); });
 
     return zones;
-}
\ No newline at end of file
+}
+
+bool DeckListModel::isCardLegalForCurrentFormat(const CardInfoPtr cardInfo)
+{
+    if (!deckList->getGameFormat().isEmpty()) {
+        if (cardInfo->getProperties().contains("format-" + deckList->getGameFormat())) {
+            QString formatLegality = cardInfo->getProperty("format-" + deckList->getGameFormat());
+            return formatLegality == "legal" || formatLegality == "restricted";
+        }
+        return false;
+    }
+    return true;
+}
+
+int maxAllowedForLegality(const FormatRules &format, const QString &legality)
+{
+    for (const AllowedCount &c : format.allowedCounts) {
+        if (c.label == legality) {
+            return c.max;
+        }
+    }
+    return -1; // unknown legality → treat as illegal
+}
+
+
+bool DeckListModel::isCardQuantityLegalForCurrentFormat(const CardInfoPtr cardInfo, int quantity)
+{
+    auto formatRules = CardDatabaseManager::query()->getFormat(deckList->getGameFormat());
+
+    if (!formatRules) {
+        return true;
+    }
+
+    // Exceptions always win
+    if (cardHasAnyException(*cardInfo, *formatRules)) {
+        return true;
+    }
+
+    const QString legalityProp = "format-" + deckList->getGameFormat();
+    if (!cardInfo->getProperties().contains(legalityProp)) {
+        return false;
+    }
+
+    const QString legality = cardInfo->getProperty(legalityProp);
+
+    int maxAllowed = maxAllowedForLegality(*formatRules, legality);
+
+    if (maxAllowed == -1) {
+        return false;
+    }
+
+    if (maxAllowed < 0) { // unlimited
+        return true;
+    }
+
+    return quantity <= maxAllowed;
+}
+
+void DeckListModel::refreshCardFormatLegalities()
+{
+    InnerDecklistNode *listRoot = deckList->getRoot();
+
+    for (int i = 0; i < listRoot->size(); i++) {
+        auto *currentZone = static_cast<InnerDecklistNode *>(listRoot->at(i));
+        for (int j = 0; j < currentZone->size(); j++) {
+            auto *currentCard = static_cast<DecklistCardNode *>(currentZone->at(j));
+
+            // TODO: better sanity checking
+            if (currentCard == nullptr) {
+                continue;
+            }
+
+            ExactCard exactCard = CardDatabaseManager::query()->getCard(currentCard->toCardRef());
+            if (!exactCard) {
+                continue;
+            }
+
+            bool legal = isCardLegalForCurrentFormat(exactCard.getCardPtr());
+
+            if (legal) {
+                legal = isCardQuantityLegalForCurrentFormat(exactCard.getCardPtr(), currentCard->getNumber());
+            }
+
+            currentCard->setFormatLegality(legal);
+        }
+    }
+}
diff --git a/libcockatrice_models/libcockatrice/models/deck_list/deck_list_model.h b/libcockatrice_models/libcockatrice/models/deck_list/deck_list_model.h
index 0b47faed4..c03497bd5 100644
--- a/libcockatrice_models/libcockatrice/models/deck_list/deck_list_model.h
+++ b/libcockatrice_models/libcockatrice/models/deck_list/deck_list_model.h
@@ -164,6 +164,14 @@ public:
     {
         dataNode->setCardCollectorNumber(_cardSetNumber);
     }
+    bool getFormatLegality() const override
+    {
+        return dataNode->getFormatLegality();
+    }
+    void setFormatLegality(const bool _formatLegal) override
+    {
+        dataNode->setFormatLegality(_formatLegal);
+    }
 
     /**
      * @brief Returns the underlying data node.
@@ -209,6 +217,9 @@ public slots:
      */
     void rebuildTree();
 
+public slots:
+    void setActiveFormat(const QString &_format);
+
 signals:
     /**
      * @brief Emitted whenever the deck hash changes due to modifications in the model.
@@ -301,6 +312,9 @@ public:
     [[nodiscard]] QList<ExactCard> getCards() const;
     [[nodiscard]] QList<ExactCard> getCardsForZone(const QString &zoneName) const;
     [[nodiscard]] QList<QString> getZones() const;
+    bool isCardLegalForCurrentFormat(CardInfoPtr cardInfo);
+    bool isCardQuantityLegalForCurrentFormat(CardInfoPtr cardInfo, int quantity);
+    void refreshCardFormatLegalities();
 
     /**
      * @brief Sets the criteria used to group cards in the model.
diff --git a/oracle/src/oracleimporter.cpp b/oracle/src/oracleimporter.cpp
index f316e439d..813df49ae 100644
--- a/oracle/src/oracleimporter.cpp
+++ b/oracle/src/oracleimporter.cpp
@@ -13,6 +13,10 @@
 #include <libcockatrice/card/database/parser/cockatrice_xml_4.h>
 #include <libcockatrice/card/relation/card_relation.h>
 
+static const QList<AllowedCount> kConstructedCounts = {{4, "legal"}, {0, "banned"}};
+
+static const QList<AllowedCount> kSingletonCounts = {{1, "legal"}, {0, "banned"}};
+
 SplitCardPart::SplitCardPart(const QString &_name,
                              const QString &_text,
                              const QVariantHash &_properties,
@@ -463,6 +467,71 @@ int OracleImporter::importCardsFromSet(const CardSetPtr &currentSet, const QList
     return numCards;
 }
 
+FormatRulesNameMap OracleImporter::createDefaultMagicFormats()
+{
+    // Predefined common exceptions
+    CardCondition superTypeIsBasic;
+    superTypeIsBasic.field = "type";
+    superTypeIsBasic.matchType = "contains";
+    superTypeIsBasic.value = "Basic Land";
+
+    ExceptionRule basicLands;
+    basicLands.conditions.append(superTypeIsBasic);
+
+    CardCondition anyNumberAllowed;
+    anyNumberAllowed.field = "text";
+    anyNumberAllowed.matchType = "contains";
+    anyNumberAllowed.value = "A deck can have any number of";
+
+    ExceptionRule mayContainAnyNumber;
+    mayContainAnyNumber.conditions.append(anyNumberAllowed);
+
+    // Map to store default rules
+    FormatRulesNameMap defaultFormatRulesNameMap;
+
+    // ----------------- Helper lambda to create format -----------------
+    auto makeFormat = [&](const QString &name, int minDeck = 60, int maxDeck = -1, int maxSideboardSize = 15,
+                          const QList<AllowedCount> &allowedCounts = kConstructedCounts) -> FormatRulesPtr {
+        FormatRulesPtr f(new FormatRules);
+        f->formatName = name;
+        f->allowedCounts = allowedCounts;
+        f->minDeckSize = minDeck;
+        f->maxDeckSize = maxDeck;
+        f->maxSideboardSize = maxSideboardSize;
+        f->exceptions.append(basicLands);
+        f->exceptions.append(mayContainAnyNumber);
+        defaultFormatRulesNameMap.insert(name.toLower(), f);
+        return f;
+    };
+
+    // ----------------- Standard formats -----------------
+    makeFormat("Standard");
+    makeFormat("Modern");
+    makeFormat("Legacy");
+    makeFormat("Pioneer");
+    makeFormat("Historic");
+    makeFormat("Timeless");
+    makeFormat("Future");
+    makeFormat("OldSchool");
+    makeFormat("Premodern");
+    makeFormat("Pauper");
+    makeFormat("Penny");
+
+    // ----------------- Singleton formats -----------------
+    makeFormat("Commander", 100, 100, 15, kSingletonCounts);
+    makeFormat("Duel", 100, 100, 15, kSingletonCounts);
+    makeFormat("Brawl", 60, 60, 15, kSingletonCounts);
+    makeFormat("StandardBrawl", 60, 60, 15, kSingletonCounts);
+    makeFormat("Oathbreaker", 60, 60, 15, kSingletonCounts);
+    makeFormat("PauperCommander", 100, 100, 15, kSingletonCounts);
+    makeFormat("Predh", 100, 100, 15, kSingletonCounts);
+
+    // ----------------- Restricted formats -----------------
+    makeFormat("Vintage", 60, -1, 15, {{4, "legal"}, {1, "restricted"}, {0, "banned"}});
+
+    return defaultFormatRulesNameMap;
+}
+
 int OracleImporter::startImport()
 {
     static ICardSetPriorityController *noOpController = new NoopCardSetPriorityController();
@@ -497,7 +566,8 @@ int OracleImporter::startImport()
 bool OracleImporter::saveToFile(const QString &fileName, const QString &sourceUrl, const QString &sourceVersion)
 {
     CockatriceXml4Parser parser(new NoopCardPreferenceProvider());
-    return parser.saveToFile(sets, cards, fileName, sourceUrl, sourceVersion);
+
+    return parser.saveToFile(createDefaultMagicFormats(), sets, cards, fileName, sourceUrl, sourceVersion);
 }
 
 void OracleImporter::clear()
diff --git a/oracle/src/oracleimporter.h b/oracle/src/oracleimporter.h
index 3ec6da6e1..e83958d73 100644
--- a/oracle/src/oracleimporter.h
+++ b/oracle/src/oracleimporter.h
@@ -154,6 +154,7 @@ public:
     int startImport();
     bool saveToFile(const QString &fileName, const QString &sourceUrl, const QString &sourceVersion);
     int importCardsFromSet(const CardSetPtr &currentSet, const QList<QVariant> &cardsList);
+    FormatRulesNameMap createDefaultMagicFormats();
     const CardNameMap &getCardList() const
     {
         return cards;