diff --git a/Libraries/Utilities/HMRClient.js b/Libraries/Utilities/HMRClient.js
index 6a56826866e24a..b37f5961d2e0b3 100644
--- a/Libraries/Utilities/HMRClient.js
+++ b/Libraries/Utilities/HMRClient.js
@@ -241,9 +241,23 @@ Error: ${e.message}`;
       }
     });
 
-    client.on('close', data => {
+    client.on('close', closeEvent => {
       LoadingView.hide();
-      setHMRUnavailableReason('Disconnected from Metro.');
+
+      // https://www.rfc-editor.org/rfc/rfc6455.html#section-7.4.1
+      // https://www.rfc-editor.org/rfc/rfc6455.html#section-7.1.5
+      const isNormalOrUnsetCloseReason =
+        closeEvent.code === 1000 ||
+        closeEvent.code === 1005 ||
+        closeEvent.code == null;
+
+      if (isNormalOrUnsetCloseReason) {
+        setHMRUnavailableReason('Disconnected from Metro.');
+      } else {
+        setHMRUnavailableReason(
+          `Disconnected from Metro (${closeEvent.code}: "${closeEvent.reason}").`,
+        );
+      }
     });
 
     if (isEnabled) {
diff --git a/Libraries/WebSocket/WebSocket.js b/Libraries/WebSocket/WebSocket.js
index b2093b3af28a4b..3fdde2b3639adf 100644
--- a/Libraries/WebSocket/WebSocket.js
+++ b/Libraries/WebSocket/WebSocket.js
@@ -43,6 +43,10 @@ const CLOSED = 3;
 
 const CLOSE_NORMAL = 1000;
 
+// Abnormal closure where no code is provided in a control frame
+// https://www.rfc-editor.org/rfc/rfc6455.html#section-7.1.5
+const CLOSE_ABNORMAL = 1006;
+
 const WEBSOCKET_EVENTS = ['close', 'error', 'message', 'open'];
 
 let nextWebSocketId = 0;
@@ -260,6 +264,7 @@ class WebSocket extends (EventTarget(...WEBSOCKET_EVENTS): any) {
           new WebSocketEvent('close', {
             code: ev.code,
             reason: ev.reason,
+            // TODO: missing `wasClean` (exposed on iOS as `clean` but missing on Android)
           }),
         );
         this._unregisterEvents();
@@ -277,7 +282,9 @@ class WebSocket extends (EventTarget(...WEBSOCKET_EVENTS): any) {
         );
         this.dispatchEvent(
           new WebSocketEvent('close', {
-            message: ev.message,
+            code: CLOSE_ABNORMAL,
+            reason: ev.message,
+            // TODO: Expose `wasClean`
           }),
         );
         this._unregisterEvents();