diff --git a/changelog.d/notifications-group-key.add b/changelog.d/notifications-group-key.add
new file mode 100644
index 0000000000..386927f4a4
--- /dev/null
+++ b/changelog.d/notifications-group-key.add
@@ -0,0 +1 @@
+Add `group_key` to notifications
\ No newline at end of file
diff --git a/lib/pleroma/web/api_spec/operations/notification_operation.ex b/lib/pleroma/web/api_spec/operations/notification_operation.ex
index 51e41beed6..b0d0e39503 100644
--- a/lib/pleroma/web/api_spec/operations/notification_operation.ex
+++ b/lib/pleroma/web/api_spec/operations/notification_operation.ex
@@ -157,6 +157,10 @@ def notification do
       type: :object,
       properties: %{
         id: %Schema{type: :string},
+        group_key: %Schema{
+          type: :string,
+          description: "Group key shared by similar notifications"
+        },
         type: notification_type(),
         created_at: %Schema{type: :string, format: :"date-time"},
         account: %Schema{
@@ -184,6 +188,7 @@ def notification do
       },
       example: %{
         "id" => "34975861",
+        "group-key" => "ungrouped-34975861",
         "type" => "mention",
         "created_at" => "2019-11-23T07:49:02.064Z",
         "account" => Account.schema().example,
diff --git a/lib/pleroma/web/mastodon_api/views/notification_view.ex b/lib/pleroma/web/mastodon_api/views/notification_view.ex
index ff84738505..41df5fdea6 100644
--- a/lib/pleroma/web/mastodon_api/views/notification_view.ex
+++ b/lib/pleroma/web/mastodon_api/views/notification_view.ex
@@ -95,6 +95,7 @@ def render(
 
     response = %{
       id: to_string(notification.id),
+      group_key: "ungrouped-" <> to_string(notification.id),
       type: notification.type,
       created_at: CommonAPI.Utils.to_masto_date(notification.inserted_at),
       account: account,
diff --git a/test/pleroma/web/mastodon_api/views/notification_view_test.exs b/test/pleroma/web/mastodon_api/views/notification_view_test.exs
index d806548fc5..eb3d53f3c2 100644
--- a/test/pleroma/web/mastodon_api/views/notification_view_test.exs
+++ b/test/pleroma/web/mastodon_api/views/notification_view_test.exs
@@ -56,6 +56,7 @@ test "ChatMessage notification" do
 
     expected = %{
       id: to_string(notification.id),
+      group_key: "ungrouped-#{to_string(notification.id)}",
       pleroma: %{is_seen: false, is_muted: false},
       type: "pleroma:chat_mention",
       account: AccountView.render("show.json", %{user: user, for: recipient}),
@@ -75,6 +76,7 @@ test "Mention notification" do
 
     expected = %{
       id: to_string(notification.id),
+      group_key: "ungrouped-#{to_string(notification.id)}",
       pleroma: %{is_seen: false, is_muted: false},
       type: "mention",
       account:
@@ -99,6 +101,7 @@ test "Favourite notification" do
 
     expected = %{
       id: to_string(notification.id),
+      group_key: "ungrouped-#{to_string(notification.id)}",
       pleroma: %{is_seen: false, is_muted: false},
       type: "favourite",
       account: AccountView.render("show.json", %{user: another_user, for: user}),
@@ -119,6 +122,7 @@ test "Reblog notification" do
 
     expected = %{
       id: to_string(notification.id),
+      group_key: "ungrouped-#{to_string(notification.id)}",
       pleroma: %{is_seen: false, is_muted: false},
       type: "reblog",
       account: AccountView.render("show.json", %{user: another_user, for: user}),
@@ -137,6 +141,7 @@ test "Follow notification" do
 
     expected = %{
       id: to_string(notification.id),
+      group_key: "ungrouped-#{to_string(notification.id)}",
       pleroma: %{is_seen: false, is_muted: false},
       type: "follow",
       account: AccountView.render("show.json", %{user: follower, for: followed}),
@@ -166,6 +171,7 @@ test "Move notification" do
 
     expected = %{
       id: to_string(notification.id),
+      group_key: "ungrouped-#{to_string(notification.id)}",
       pleroma: %{is_seen: false, is_muted: false},
       type: "move",
       account: AccountView.render("show.json", %{user: old_user, for: follower}),
@@ -191,6 +197,7 @@ test "EmojiReact notification" do
 
     expected = %{
       id: to_string(notification.id),
+      group_key: "ungrouped-#{to_string(notification.id)}",
       pleroma: %{is_seen: false, is_muted: false},
       type: "pleroma:emoji_reaction",
       emoji: "☕",
@@ -230,6 +237,7 @@ test "EmojiReact custom emoji notification" do
 
     expected = %{
       id: to_string(notification.id),
+      group_key: "ungrouped-#{to_string(notification.id)}",
       pleroma: %{is_seen: false, is_muted: false},
       type: "pleroma:emoji_reaction",
       emoji: ":dinosaur:",
@@ -249,6 +257,7 @@ test "Poll notification" do
 
     expected = %{
       id: to_string(notification.id),
+      group_key: "ungrouped-#{to_string(notification.id)}",
       pleroma: %{is_seen: false, is_muted: false},
       type: "poll",
       account:
@@ -275,6 +284,7 @@ test "Report notification" do
 
     expected = %{
       id: to_string(notification.id),
+      group_key: "ungrouped-#{to_string(notification.id)}",
       pleroma: %{is_seen: false, is_muted: false},
       type: "pleroma:report",
       account: AccountView.render("show.json", %{user: reporting_user, for: moderator_user}),
@@ -301,6 +311,7 @@ test "Edit notification" do
 
     expected = %{
       id: to_string(notification.id),
+      group_key: "ungrouped-#{to_string(notification.id)}",
       pleroma: %{is_seen: false, is_muted: false},
       type: "update",
       account: AccountView.render("show.json", %{user: user, for: repeat_user}),
@@ -323,6 +334,7 @@ test "muted notification" do
 
     expected = %{
       id: to_string(notification.id),
+      group_key: "ungrouped-#{to_string(notification.id)}",
       pleroma: %{is_seen: true, is_muted: true},
       type: "favourite",
       account: AccountView.render("show.json", %{user: another_user, for: user}),
@@ -346,6 +358,7 @@ test "Subscribed status notification" do
 
     expected = %{
       id: to_string(notification.id),
+      group_key: "ungrouped-#{to_string(notification.id)}",
       pleroma: %{is_seen: false, is_muted: false},
       type: "status",
       account: