diff --git a/src/vs/workbench/contrib/browserView/electron-browser/browserView.contribution.ts b/src/vs/workbench/contrib/browserView/electron-browser/browserView.contribution.ts
index e48ef83bf1bd..7a69461a8f94 100644
--- a/src/vs/workbench/contrib/browserView/electron-browser/browserView.contribution.ts
+++ b/src/vs/workbench/contrib/browserView/electron-browser/browserView.contribution.ts
@@ -108,7 +108,7 @@ class BrowserEditorResolverContribution implements IWorkbenchContribution {
 			}
 		);
 
-		for (const extension of ['html', 'htm']) {
+		for (const extension of ['html', 'htm', 'mhtml', 'mht']) {
 			editorResolverService.registerEditor(
 				`${Schemas.file}:/**/*.${extension}`,
 				{
diff --git a/src/vs/workbench/contrib/browserView/electron-browser/features/browserTabManagementFeatures.ts b/src/vs/workbench/contrib/browserView/electron-browser/features/browserTabManagementFeatures.ts
index 8c0dfd27b3bf..471aed562410 100644
--- a/src/vs/workbench/contrib/browserView/electron-browser/features/browserTabManagementFeatures.ts
+++ b/src/vs/workbench/contrib/browserView/electron-browser/features/browserTabManagementFeatures.ts
@@ -340,9 +340,9 @@ class OpenIntegratedBrowserAction extends Action2 {
 
 class OpenFileInIntegratedBrowserAction extends Action2 {
 	constructor() {
-		const IS_LOCAL_HTML_FILE = ContextKeyExpr.and(
+		const IS_SUPPORTED_LOCAL_BROWSER_FILE = ContextKeyExpr.and(
 			ResourceContextKey.Scheme.isEqualTo(Schemas.file),
-			ContextKeyExpr.regex(ResourceContextKey.Extension.key, /\.html?$/i),
+			ContextKeyExpr.regex(ResourceContextKey.Extension.key, /\.(?:html?|mht(?:ml)?)$/i),
 		);
 		super({
 			id: BrowserViewCommandId.OpenFile,
@@ -350,25 +350,25 @@ class OpenFileInIntegratedBrowserAction extends Action2 {
 			category: BrowserActionCategory,
 			icon: Codicon.globe,
 			f1: true,
-			precondition: IS_LOCAL_HTML_FILE,
+			precondition: IS_SUPPORTED_LOCAL_BROWSER_FILE,
 			menu: [
 				{
 					id: MenuId.ExplorerContext,
 					group: 'navigation',
 					order: 29,
-					when: IS_LOCAL_HTML_FILE,
+					when: IS_SUPPORTED_LOCAL_BROWSER_FILE,
 				},
 				{
 					id: MenuId.EditorTitleContext,
 					group: '1_open',
 					order: 5,
-					when: IS_LOCAL_HTML_FILE,
+					when: IS_SUPPORTED_LOCAL_BROWSER_FILE,
 				},
 				{
 					id: MenuId.EditorTitle,
 					group: 'navigation',
 					order: 99,
-					when: IS_LOCAL_HTML_FILE,
+					when: IS_SUPPORTED_LOCAL_BROWSER_FILE,
 				},
 			]
 		});