diff --git a/Libraries/LibWeb/HTML/EventLoop/EventLoop.cpp b/Libraries/LibWeb/HTML/EventLoop/EventLoop.cpp
index 6b5d0f72ee0..1093c7e7bc5 100644
--- a/Libraries/LibWeb/HTML/EventLoop/EventLoop.cpp
+++ b/Libraries/LibWeb/HTML/EventLoop/EventLoop.cpp
@@ -21,6 +21,7 @@
 #include <LibWeb/HTML/Window.h>
 #include <LibWeb/HighResolutionTime/Performance.h>
 #include <LibWeb/HighResolutionTime/TimeOrigin.h>
+#include <LibWeb/IndexedDB/Internal/Algorithms.h>
 #include <LibWeb/Page/Page.h>
 #include <LibWeb/Painting/PaintableBox.h>
 #include <LibWeb/Painting/ViewportPaintable.h>
@@ -599,7 +600,8 @@ void EventLoop::perform_a_microtask_checkpoint()
         global->notify_about_rejected_promises({});
     }
 
-    // FIXME: 5. Cleanup Indexed Database transactions.
+    // 5. Cleanup Indexed Database transactions.
+    IndexedDB::cleanup_indexed_database_transactions(*this);
 
     // 6. Perform ClearKeptObjects().
     vm().finish_execution_generation();
diff --git a/Libraries/LibWeb/IndexedDB/IDBTransaction.h b/Libraries/LibWeb/IndexedDB/IDBTransaction.h
index 08040edede4..4b486ba6d7a 100644
--- a/Libraries/LibWeb/IndexedDB/IDBTransaction.h
+++ b/Libraries/LibWeb/IndexedDB/IDBTransaction.h
@@ -47,6 +47,7 @@ public:
     [[nodiscard]] RequestList& request_list() { return m_request_list; }
     [[nodiscard]] ReadonlySpan<GC::Ref<ObjectStore>> scope() const { return m_scope; }
     [[nodiscard]] String uuid() const { return m_uuid; }
+    [[nodiscard]] GC::Ptr<HTML::EventLoop> cleanup_event_loop() const { return m_cleanup_event_loop; }
 
     void set_mode(Bindings::IDBTransactionMode mode) { m_mode = mode; }
     void set_error(GC::Ptr<WebIDL::DOMException> error) { m_error = error; }
diff --git a/Libraries/LibWeb/IndexedDB/Internal/Algorithms.cpp b/Libraries/LibWeb/IndexedDB/Internal/Algorithms.cpp
index 5f953a082e8..ae9f7b3ae68 100644
--- a/Libraries/LibWeb/IndexedDB/Internal/Algorithms.cpp
+++ b/Libraries/LibWeb/IndexedDB/Internal/Algorithms.cpp
@@ -2051,4 +2051,32 @@ void queue_a_database_task(GC::Ref<GC::Function<void()>> steps)
     HTML::queue_a_task(HTML::Task::Source::DatabaseAccess, nullptr, nullptr, steps);
 }
 
+// https://w3c.github.io/IndexedDB/#cleanup-indexed-database-transactions
+bool cleanup_indexed_database_transactions(GC::Ref<HTML::EventLoop> event_loop)
+{
+    bool has_matching_event_loop = false;
+
+    Database::for_each_database([&has_matching_event_loop, event_loop](GC::Root<Database> const& database) {
+        for (auto const& connection : database->associated_connections()) {
+            for (auto const& transaction : connection->transactions()) {
+
+                // 2. For each transaction transaction with cleanup event loop matching the current event loop:
+                if (transaction->cleanup_event_loop() == event_loop) {
+                    has_matching_event_loop = true;
+
+                    // 1. Set transaction’s state to inactive.
+                    transaction->set_state(IDBTransaction::TransactionState::Inactive);
+
+                    // 2. Clear transaction’s cleanup event loop.
+                    transaction->set_cleanup_event_loop(nullptr);
+                }
+            }
+        }
+    });
+
+    // 1. If there are no transactions with cleanup event loop matching the current event loop, return false.
+    // 3. Return true.
+    return has_matching_event_loop;
+}
+
 }
diff --git a/Libraries/LibWeb/IndexedDB/Internal/Algorithms.h b/Libraries/LibWeb/IndexedDB/Internal/Algorithms.h
index 373e77050a5..ce04060a78c 100644
--- a/Libraries/LibWeb/IndexedDB/Internal/Algorithms.h
+++ b/Libraries/LibWeb/IndexedDB/Internal/Algorithms.h
@@ -57,5 +57,6 @@ JS::Value retrieve_a_value_from_an_index(JS::Realm&, GC::Ref<Index>, GC::Ref<IDB
 GC::Ref<JS::Array> retrieve_multiple_referenced_values_from_an_index(JS::Realm&, GC::Ref<Index>, GC::Ref<IDBKeyRange>, Optional<WebIDL::UnsignedLong>);
 GC::Ref<JS::Array> retrieve_multiple_values_from_an_index(JS::Realm&, GC::Ref<Index>, GC::Ref<IDBKeyRange>, Optional<WebIDL::UnsignedLong>);
 void queue_a_database_task(GC::Ref<GC::Function<void()>>);
+bool cleanup_indexed_database_transactions(GC::Ref<HTML::EventLoop>);
 
 }
diff --git a/Libraries/LibWeb/IndexedDB/Internal/Database.cpp b/Libraries/LibWeb/IndexedDB/Internal/Database.cpp
index cf4f5fd945c..9fa881e01d4 100644
--- a/Libraries/LibWeb/IndexedDB/Internal/Database.cpp
+++ b/Libraries/LibWeb/IndexedDB/Internal/Database.cpp
@@ -14,6 +14,15 @@ namespace Web::IndexedDB {
 using IDBDatabaseMapping = HashMap<StorageAPI::StorageKey, HashMap<String, GC::Root<Database>>>;
 static IDBDatabaseMapping m_databases;
 
+void Database::for_each_database(AK::Function<void(GC::Root<Database> const&)> const& visitor)
+{
+    for (auto const& [key, mapping] : m_databases) {
+        for (auto const& database_mapping : mapping) {
+            visitor(database_mapping.value);
+        }
+    }
+}
+
 GC_DEFINE_ALLOCATOR(Database);
 
 Database::~Database() = default;
diff --git a/Libraries/LibWeb/IndexedDB/Internal/Database.h b/Libraries/LibWeb/IndexedDB/Internal/Database.h
index ebc5c24485d..721a61855f5 100644
--- a/Libraries/LibWeb/IndexedDB/Internal/Database.h
+++ b/Libraries/LibWeb/IndexedDB/Internal/Database.h
@@ -53,6 +53,8 @@ public:
     [[nodiscard]] static ErrorOr<GC::Root<Database>> create_for_key_and_name(JS::Realm&, StorageAPI::StorageKey&, String&);
     [[nodiscard]] static ErrorOr<void> delete_for_key_and_name(StorageAPI::StorageKey&, String&);
 
+    static void for_each_database(AK::Function<void(GC::Root<Database> const&)> const& visitor);
+
     [[nodiscard]] static GC::Ref<Database> create(JS::Realm&, String const&);
     virtual ~Database();