diff --git a/bin/dart_fidl_json/test/fidl/dart.fidl.json.test/types.fidl b/bin/dart_fidl_json/test/fidl/dart.fidl.json.test/types.fidl
index 088f00e..86f6f3c 100644
--- a/bin/dart_fidl_json/test/fidl/dart.fidl.json.test/types.fidl
+++ b/bin/dart_fidl_json/test/fidl/dart.fidl.json.test/types.fidl
@@ -21,4 +21,4 @@
   val1 = 1;
   val2 = 2;
   val3 = 3;
-};
\ No newline at end of file
+};
diff --git a/bin/fidl_bindings_test/fidl/bindings_test.fidl b/bin/fidl_bindings_test/fidl/bindings_test.fidl
index 9dcb381..480b679 100644
--- a/bin/fidl_bindings_test/fidl/bindings_test.fidl
+++ b/bin/fidl_bindings_test/fidl/bindings_test.fidl
@@ -29,7 +29,7 @@
 };
 
 [Discoverable]
-interface TestServer {
+protocol TestServer {
     OneWayNoArgs();
     ReceivedOneWayNoArgs() -> (bool received);
 
@@ -98,6 +98,6 @@
     uint32 baz;
 };
 
-interface SimpleServer {
+protocol SimpleServer {
     Ping() -> ();
 };
diff --git a/bin/ui/skottie_viewer/skottie_loader.fidl b/bin/ui/skottie_viewer/skottie_loader.fidl
index 390b5a3..79a6cfe 100644
--- a/bin/ui/skottie_viewer/skottie_loader.fidl
+++ b/bin/ui/skottie_viewer/skottie_loader.fidl
@@ -22,7 +22,7 @@
 
 // Defines the player interface to control the animation. It is returned upon
 // successful load of the animation.
-interface Player {
+protocol Player {
     // Seek to position |t| where 0 <= t <= 1.
     Seek(float32 t);
     // Play and stop at |t| = 1 if |loop| = false.
@@ -34,7 +34,7 @@
 [Discoverable]
 // Skottie loader exported by |ViewProvider| to load skottie JSON animations
 // into views created from it.
-interface Loader {
+protocol Loader {
     // Load the snapshot from the Vmo buffer payload. Returns a callback with
     // |Player| controller and load status |Status|. |player| is null if loading
     // failed.
diff --git a/bin/ui/text_input_mod/public/fidl/textinputmod.fidl b/bin/ui/text_input_mod/public/fidl/textinputmod.fidl
index b02a79e..13abe7b 100644
--- a/bin/ui/text_input_mod/public/fidl/textinputmod.fidl
+++ b/bin/ui/text_input_mod/public/fidl/textinputmod.fidl
@@ -5,12 +5,12 @@
 library fuchsia.textinputmod;
 
 [Discoverable]
-interface TextInputModReceiver {
+protocol TextInputModReceiver {
     UserEnteredText(string text) -> ();
     UserCanceled() -> ();
 };
 
 [Discoverable]
-interface TextInputMod {
+protocol TextInputMod {
     ListenForTextInput(TextInputModReceiver receiver) -> ();
 };
diff --git a/bin/xi/xi_session_agent/fidl/xi_session.fidl b/bin/xi/xi_session_agent/fidl/xi_session.fidl
index 86f5f23..ec4e491 100644
--- a/bin/xi/xi_session_agent/fidl/xi_session.fidl
+++ b/bin/xi/xi_session_agent/fidl/xi_session.fidl
@@ -6,7 +6,7 @@
 
 // Interface for the proof-of-concept xi_session_manager service.
 [Discoverable]
-interface XiSessionManager {
+protocol XiSessionManager {
     NewSession() -> (string session_id);
     CloseSession(string session_id);
     ConnectSession(string session_id, handle<socket> sock);
diff --git a/examples/tictactoe/public/fidl/tictactoe/game_tracker.fidl b/examples/tictactoe/public/fidl/tictactoe/game_tracker.fidl
index 044239b..7826b21 100644
--- a/examples/tictactoe/public/fidl/tictactoe/game_tracker.fidl
+++ b/examples/tictactoe/public/fidl/tictactoe/game_tracker.fidl
@@ -22,7 +22,7 @@
 };
 
 [Discoverable]
-interface GameTracker {
+protocol GameTracker {
     RecordWin(Player player) -> (ExecuteResult result);
 
     // Request that the game tracker start sending score updates to the message
diff --git a/public/dart/fuchsia_modular/examples/fidl/fibonacci_service.fidl b/public/dart/fuchsia_modular/examples/fidl/fibonacci_service.fidl
index a9c4318..0859f7d 100644
--- a/public/dart/fuchsia_modular/examples/fidl/fibonacci_service.fidl
+++ b/public/dart/fuchsia_modular/examples/fidl/fibonacci_service.fidl
@@ -5,6 +5,6 @@
 library fuchsia.fibonacci;
 
 [Discoverable]
-interface FibonacciService {
+protocol FibonacciService {
     CalcFibonacci(uint32 n) -> (uint32 result);
 };
diff --git a/public/dart/fuchsia_services/examples/mind_reader/fidl/mind_reader.fidl b/public/dart/fuchsia_services/examples/mind_reader/fidl/mind_reader.fidl
index af22ccd..1881904 100644
--- a/public/dart/fuchsia_services/examples/mind_reader/fidl/mind_reader.fidl
+++ b/public/dart/fuchsia_services/examples/mind_reader/fidl/mind_reader.fidl
@@ -5,14 +5,14 @@
 library fuchsia.services.examples;
 
 [Discoverable]
-interface MindReader {
+protocol MindReader {
   /// When this method is called the service will attempt to guess
   /// what the calling process is thinking.
   ReadMind() -> (string response);
 };
 
 [Discoverable]
-interface ThoughtLeaker {
+protocol ThoughtLeaker {
   /// This service is used to leak the current thought of the process.
   /// If this service is exposed to the [MindReader] it will connect
   /// to it to extract the current thought.
diff --git a/runtime/dart_runner/examples/hello_app_dart/interfaces/hello.fidl b/runtime/dart_runner/examples/hello_app_dart/interfaces/hello.fidl
index 72dec65..65c7884 100644
--- a/runtime/dart_runner/examples/hello_app_dart/interfaces/hello.fidl
+++ b/runtime/dart_runner/examples/hello_app_dart/interfaces/hello.fidl
@@ -5,6 +5,6 @@
 library fuchsia.examples.hello;
 
 [Discoverable]
-interface Hello {
+protocol Hello {
     Say(string request) -> (string response);
 };