lib/pleroma/web/mastodon_api/views/instance_view.ex

@@ -14,7 +14,7 @@ def render("show.json", _) do
     instance = Config.get(:instance)
 
     %{
-      uri: Pleroma.Web.Endpoint.url(),
+      uri: Pleroma.Web.WebFinger.domain(),
       title: Keyword.get(instance, :name),
       description: Keyword.get(instance, :description),
       short_description:

test/pleroma/web/mastodon_api/controllers/instance_controller_test.exs

@@ -18,9 +18,12 @@ test "get instance information", %{conn: conn} do
     thumbnail = Pleroma.Web.Endpoint.url() <> Pleroma.Config.get([:instance, :instance_thumbnail])
     background = Pleroma.Web.Endpoint.url() <> Pleroma.Config.get([:instance, :background_image])
 
+    # if no WebFinger domain is configured (without protocol)
+    uri = Pleroma.Web.Endpoint.host()
+
     # Note: not checking for "max_toot_chars" since it's optional
     assert %{
-             "uri" => _,
+             "uri" => ^uri,
              "title" => _,
              "description" => _,
              "short_description" => _,
@@ -55,6 +58,15 @@ test "get instance information", %{conn: conn} do
     assert background == from_config_background
   end
 
+  test "get instance information prefers WebFinger domain for uri", %{conn: conn} do
+    webfinger_domain = "webfinger.example"
+    clear_config([Pleroma.Web.WebFinger, :domain], webfinger_domain)
+    conn = get(conn, "/api/v1/instance")
+
+    assert result = json_response_and_validate_schema(conn, 200)
+    assert match?(%{"uri" => ^webfinger_domain}, result)
+  end
+
   test "get instance stats", %{conn: conn} do
     user = insert(:user, %{local: true})