diff --git a/packages/mini-browser/src/browser/mini-browser-open-handler.ts b/packages/mini-browser/src/browser/mini-browser-open-handler.ts
index be664c324116d..95df96ff5d865 100644
--- a/packages/mini-browser/src/browser/mini-browser-open-handler.ts
+++ b/packages/mini-browser/src/browser/mini-browser-open-handler.ts
@@ -159,7 +159,12 @@ export class MiniBrowserOpenHandler extends NavigatableWidgetOpenHandler<MiniBro
 
     protected resetBackground(uri: URI): MaybePromise<boolean> {
         const { scheme } = uri;
-        return scheme === 'http' || scheme === 'https' || (scheme === 'file' && uri.toString().endsWith('.html'));
+        const uriStr = uri.toString();
+        return scheme === 'http'
+            || scheme === 'https'
+            || (scheme === 'file'
+                && (uriStr.endsWith('html') || uriStr.endsWith('.htm'))
+            );
     }
 
     protected async defaultOptions(): Promise<MiniBrowserOpenerOptions & { widgetOptions: ApplicationShell.WidgetOptions }> {
diff --git a/packages/mini-browser/src/node/mini-browser-endpoint.ts b/packages/mini-browser/src/node/mini-browser-endpoint.ts
index bdb22d8b28a58..ae3a1a4721a5a 100644
--- a/packages/mini-browser/src/node/mini-browser-endpoint.ts
+++ b/packages/mini-browser/src/node/mini-browser-endpoint.ts
@@ -198,8 +198,8 @@ const CODE_EDITOR_PRIORITY = 100;
 @injectable()
 export class HtmlHandler implements MiniBrowserEndpointHandler {
 
-    supportedExtensions(): string {
-        return 'html';
+    supportedExtensions(): string[] {
+        return ['html', 'xhtml', 'htm'];
     }
 
     priority(): number {