diff --git a/Userland/Libraries/LibWeb/Forward.h b/Userland/Libraries/LibWeb/Forward.h
index 50f4846b99c..5c1dee0f699 100644
--- a/Userland/Libraries/LibWeb/Forward.h
+++ b/Userland/Libraries/LibWeb/Forward.h
@@ -353,6 +353,7 @@ class CloseWatcher;
 class CloseWatcherManager;
 class CustomElementDefinition;
 class CustomElementRegistry;
+class DataTransfer;
 class DataTransferItem;
 class DataTransferItemList;
 class DecodedImageData;
diff --git a/Userland/Libraries/LibWeb/HTML/DataTransfer.cpp b/Userland/Libraries/LibWeb/HTML/DataTransfer.cpp
index 770d5f1318b..45d377464ab 100644
--- a/Userland/Libraries/LibWeb/HTML/DataTransfer.cpp
+++ b/Userland/Libraries/LibWeb/HTML/DataTransfer.cpp
@@ -13,6 +13,14 @@ namespace Web::HTML {
 
 JS_DEFINE_ALLOCATOR(DataTransfer);
 
+namespace DataTransferEffect {
+
+#define __ENUMERATE_DATA_TRANSFER_EFFECT(name) FlyString name = #name##_fly_string;
+ENUMERATE_DATA_TRANSFER_EFFECTS
+#undef __ENUMERATE_DATA_TRANSFER_EFFECT
+
+}
+
 JS::NonnullGCPtr<DataTransfer> DataTransfer::construct_impl(JS::Realm& realm)
 {
     return realm.heap().allocate<DataTransfer>(realm, realm);
@@ -31,4 +39,42 @@ void DataTransfer::initialize(JS::Realm& realm)
     WEB_SET_PROTOTYPE_FOR_INTERFACE(DataTransfer);
 }
 
+void DataTransfer::set_drop_effect(String const& drop_effect)
+{
+    set_drop_effect(FlyString { drop_effect });
+}
+
+void DataTransfer::set_drop_effect(FlyString drop_effect)
+{
+    using namespace DataTransferEffect;
+
+    // On setting, if the new value is one of "none", "copy", "link", or "move", then the attribute's current value must
+    // be set to the new value. Other values must be ignored.
+    if (drop_effect.is_one_of(none, copy, link, move))
+        m_drop_effect = AK::move(drop_effect);
+}
+
+void DataTransfer::set_effect_allowed(String const& effect_allowed)
+{
+    set_effect_allowed(FlyString { effect_allowed });
+}
+
+void DataTransfer::set_effect_allowed(FlyString effect_allowed)
+{
+    // On setting, if drag data store's mode is the read/write mode and the new value is one of "none", "copy", "copyLink",
+    // "copyMove", "link", "linkMove", "move", "all", or "uninitialized", then the attribute's current value must be set
+    // to the new value. Otherwise, it must be left unchanged.
+    if (m_associated_drag_data_store.has_value() && m_associated_drag_data_store->mode() == DragDataStore::Mode::ReadWrite)
+        set_effect_allowed_internal(move(effect_allowed));
+}
+
+void DataTransfer::set_effect_allowed_internal(FlyString effect_allowed)
+{
+    // AD-HOC: We need to be able to set the effectAllowed attribute internally regardless of the state of the drag data store.
+    using namespace DataTransferEffect;
+
+    if (effect_allowed.is_one_of(none, copy, copyLink, copyMove, link, linkMove, move, all, uninitialized))
+        m_effect_allowed = AK::move(effect_allowed);
+}
+
 }
diff --git a/Userland/Libraries/LibWeb/HTML/DataTransfer.h b/Userland/Libraries/LibWeb/HTML/DataTransfer.h
index 5073a6a8943..0d1d5cf3e18 100644
--- a/Userland/Libraries/LibWeb/HTML/DataTransfer.h
+++ b/Userland/Libraries/LibWeb/HTML/DataTransfer.h
@@ -8,9 +8,30 @@
 
 #include <LibJS/Forward.h>
 #include <LibWeb/Bindings/PlatformObject.h>
+#include <LibWeb/HTML/DragDataStore.h>
 
 namespace Web::HTML {
 
+#define ENUMERATE_DATA_TRANSFER_EFFECTS        \
+    __ENUMERATE_DATA_TRANSFER_EFFECT(none)     \
+    __ENUMERATE_DATA_TRANSFER_EFFECT(copy)     \
+    __ENUMERATE_DATA_TRANSFER_EFFECT(copyLink) \
+    __ENUMERATE_DATA_TRANSFER_EFFECT(copyMove) \
+    __ENUMERATE_DATA_TRANSFER_EFFECT(link)     \
+    __ENUMERATE_DATA_TRANSFER_EFFECT(linkMove) \
+    __ENUMERATE_DATA_TRANSFER_EFFECT(move)     \
+    __ENUMERATE_DATA_TRANSFER_EFFECT(all)      \
+    __ENUMERATE_DATA_TRANSFER_EFFECT(uninitialized)
+
+namespace DataTransferEffect {
+
+#define __ENUMERATE_DATA_TRANSFER_EFFECT(name) extern FlyString name;
+ENUMERATE_DATA_TRANSFER_EFFECTS
+#undef __ENUMERATE_DATA_TRANSFER_EFFECT
+
+}
+
+// https://html.spec.whatwg.org/multipage/dnd.html#the-datatransfer-interface
 class DataTransfer : public Bindings::PlatformObject {
     WEB_PLATFORM_OBJECT(DataTransfer, Bindings::PlatformObject);
     JS_DECLARE_ALLOCATOR(DataTransfer);
@@ -19,10 +40,31 @@ public:
     static JS::NonnullGCPtr<DataTransfer> construct_impl(JS::Realm&);
     virtual ~DataTransfer() override;
 
+    FlyString const& drop_effect() const { return m_drop_effect; }
+    void set_drop_effect(String const&);
+    void set_drop_effect(FlyString);
+
+    FlyString const& effect_allowed() const { return m_effect_allowed; }
+    void set_effect_allowed(String const&);
+    void set_effect_allowed(FlyString);
+    void set_effect_allowed_internal(FlyString);
+
+    void associate_with_drag_data_store(DragDataStore& drag_data_store) { m_associated_drag_data_store = drag_data_store; }
+    void disassociate_with_drag_data_store() { m_associated_drag_data_store.clear(); }
+
 private:
     DataTransfer(JS::Realm&);
 
     virtual void initialize(JS::Realm&) override;
+
+    // https://html.spec.whatwg.org/multipage/dnd.html#dom-datatransfer-dropeffect
+    FlyString m_drop_effect { DataTransferEffect::none };
+
+    // https://html.spec.whatwg.org/multipage/dnd.html#dom-datatransfer-effectallowed
+    FlyString m_effect_allowed { DataTransferEffect::none };
+
+    // https://html.spec.whatwg.org/multipage/dnd.html#the-datatransfer-interface:drag-data-store-3
+    Optional<DragDataStore&> m_associated_drag_data_store;
 };
 
 }
diff --git a/Userland/Libraries/LibWeb/HTML/DataTransfer.idl b/Userland/Libraries/LibWeb/HTML/DataTransfer.idl
index eb43f4487a1..15afedde7e5 100644
--- a/Userland/Libraries/LibWeb/HTML/DataTransfer.idl
+++ b/Userland/Libraries/LibWeb/HTML/DataTransfer.idl
@@ -3,8 +3,8 @@
 interface DataTransfer {
     constructor();
 
-    [FIXME] attribute DOMString dropEffect;
-    [FIXME] attribute DOMString effectAllowed;
+    attribute DOMString dropEffect;
+    attribute DOMString effectAllowed;
 
     [FIXME, SameObject] readonly attribute DataTransferItemList items;