WebView2 browser flags

One of the ways you can interact with Microsoft Edge WebView2 and impact behavior is by passing browser flags (arguments, or switches) to WebView2. These browser flags are useful for testing forthcoming features, and for diagnosing issues.

For production apps, do not use these flags. During development, if the flag is present, the behavior that's specified below results.

Warning

Apps in production shouldn't use WebView2 browser flags, because these flags might be removed or altered at any time, and aren't necessarily supported long-term.

Generally, the flags are owned by both Chromium and Microsoft Edge. Chromium flags are not owned or controlled by Microsoft Edge, so Microsoft Edge doesn't have control over when or how the flags are removed or altered in their behavior.

You can set browser flags in your local device environment, or set browser flags programmatically through code. Both approaches are described below.

Setting browser flags in your local device environment

To test forthcoming features or to diagnose issues, we recommend using browser flags in your local device environment, via setting the WEBVIEW2_ADDITIONAL_BROWSER_ARGUMENTS environment variable or via registry keys. For more information, see the following Win32 API Reference: CreateCoreWebView2EnvironmentWithOptions.

Setting browser flags programmatically through code

Instead of setting browser flags in your local device environment, an alternative approach is to set browser flags programmatically, by passing the browser flags as the AdditionalBrowserArguments property of CoreWebView2EnvironmentOptions. If you set browser flags programmatically, be sure to remove the flags in code before shipping your app, to avoid accidentally shipping the flags in production.

.NET/C#

• CoreWebView2EnvironmentOptions Class:
  • CoreWebView2EnvironmentOptions.AdditionalBrowserArguments Property

WinRT/C#

• CoreWebView2EnvironmentOptions Class:
  • CoreWebView2EnvironmentOptions.AdditionalBrowserArguments Property

Win32/C++

• ICoreWebView2EnvironmentOptions:
  • ICoreWebView2EnvironmentOptions::get_AdditionalBrowserArguments
  • ICoreWebView2EnvironmentOptions::put_AdditionalBrowserArguments

See also Globals:

• CreateCoreWebView2EnvironmentWithOptions

Available WebView2 browser flags

The following WebView2 browser flags are available for use during development.

For production apps, do not use these flags. During development, if the flag is present, the behavior that's specified below results.

Flag	Description
accept-lang	Specifies Accept-Language to send to servers and expose to JavaScript via the Navigator.language DOM property. The format is language[-country], where language is the 2-letter code from ISO-639.
allow-file-access-from-files	Allows reading file:// URIs from other file:// URIs.
allow-insecure-localhost	Enables TLS/SSL errors on localhost to be ignored, so that no interstitial is done and no blocking of requests is done.
allow-run-as-system	By default, the Edge WebView browser exits if launched as System (launching as System is not recommended). This flag bypasses that check, so that even if the Edge WebView browser is launched as System, the Edge WebView browser doesn't exit.
allow-running-insecure-content	Enables insecure content in Cast Web Runtime. This flag unblocks MSPs that serve content from HTTP sources.
auto-open-devtools-for-tabs	Makes Edge WebView auto-open the DevTools window for each tab. For use by developers and by automation.
AutofillReplaceCachedWebElementsByRendererIds	Replaces cached web elements in AutofillAgent and FormTracker by their renderer IDs.
autoplay-policy	Command-line flag name to set the autoplay policy.
BlockInsecurePrivateNetworkRequests	When this feature is enabled, private network requests that are initiated from non-secure contexts in the public address space are blocked.
block-new-web-contents	Takes a true or false value. If true, makes all pop-ups and calls to window.open fail. If false, pop-ups and calls to window.open are honored.
BreakoutBoxPreferCaptureTimestampInVideoFrames	Reverts the behavior of the Timestamp property of the CoreWebView2Texture class to match legacy behavior of WebView2 Runtime version 124 and earlier.
disable-background-timer-throttling	Disables task throttling of timer tasks from background pages.
disable-domain-action-user-agent-override	Disables the per-domain User Agent override from the Domain Actions feature.
disable-gpu	Disables GPU hardware acceleration. If a software renderer isn't in place, the GPU process doesn't launch.
disable-gpu-driver-bug-workarounds	Disables workarounds for various GPU driver bugs.
disable-site-isolation-trials	Disables site isolation.
disable-web-security	Disables cross-origin policy and doesn't enforce the same-origin policy. Use for website testing only.
disk-cache-size	Forces the maximum disk space to be used by the disk cache, in bytes.
do-not-de-elevate	Prevents de-elevation of the WebView2 on launch. Used after de-elevating, to prevent infinite loops.
edge-webview-debugging-script	Runs PostWebMessage script asynchronously.
edge-webview-enable-mojo-ipcz	Enables MojoIpcz (mojo-ipcz) for apps that use WebView2.
edge-webview-foreground-boost-opt-in	Opts-in to foreground boost.
edge-webview-foreground-boost-opt-out	Opts-out of foreground boost.
edge-webview-force-personal-context	Forces Edge WebView browser processes to run in WIP personal context.
edge-webview-interactive-dragging	Enables pointer events and focus events to occur on elements that have the --app-region: drag attribute. Drag elements are interactive by default.
edge-webview-disable-interactive-dragging	Disables pointer events and focus events from occuring on elements that have the --app-region: drag attribute. If this flag isn't set, drag elements are interactive by default.
edge-webview-is-background	Indicates that WebView is being launched in the background.
edge-webview-no-dpi-workaround	Disables the "DPI awareness app compatibility shim" workaround, which launches Edge WebView browser process via a shell, so that the process doesn't inherit the "app compat" shim.
edge-webview-run-with-package-id	Runs WebView processes with a package identity (package ID) for a bridged Desktop app.
edge-webview-run-without-package-id	Runs WebView processes without a package identity (package ID) for a bridged Desktop app.
embedded-browser-webview-dpi-awareness	Sets the DPI awareness level of the server-side processes.
enable-experimental-web-platform-features	Enables Web Platform features that are in development.
enable-logging	Enable logging at the error level.
force-color-profile	Force all monitors to be treated as though they have the specified color profile. Valid values: srgb, generic-rgb.
force-device-scale-factor	Overrides the device scale factor for the Edge WebView browser UI and the contents.
force-fieldtrials	Can be used to force field trials when testing changes locally. The argument is a list of name/value pairs, separated by forward slashes. If a trial name is prefixed with an asterisk, that trial will start activated. Example: The following argument defines two trials, with the second one activated: EdgeNow/Enable/*MaterialDesignNTP/Default/. This option can also be used by the browser process to send the list of trials to a non-browser process, using the same format.
force-fieldtrial-params	Can be used to force parameters of field trials when testing changes locally. The argument is a parameter list of (key, value) pairs, prefixed by an associated (trial, group) pair. For multiple (trial, group) pairs, use a comma separator.
force-renderer-accessibility	Whether to force renderer accessibility to be on, instead of enabling renderer accessibility on-demand when a screen reader is detected. The disable-renderer-accessibility flag overrides this flag, if the disable-renderer-accessibility flag is present.
HardwareMediaKeyHandling	Enables handling of hardware media keys for controlling media.
ignore-certificate-errors	Ignores certificate-related errors.
ignore-gpu-blocklist	Whether to ignore the GPU blocklist.
incognito	Forces InPrivate (Incognito) mode even if the user data directory is specified by using the --user-data-dir flag.
isolate-origins	Require dedicated processes for a set of origins, specified as a comma-separated list. Example: --isolate-origins=https://www.foo.com,https://www.bar.com.
js-flags	Specifies the flags passed to the JS engine. Available flags: scavenger_max_new_space_capacity_mb: Specifies the maximum limit (in MB) for scavenger (minor) garbage collectors in the V8 JavaScript engine. A lower scavenger memory limit reduces memory usage, and increases the frequency of running minor garbage collectors. A higher scavenger memory limit increases memory usage, and reduces the frequency of running minor garbage collectors. Example: --js-flags=--scavenger_max_new_space_capacity_mb=8.
lang	The language file that WebView2 want to try to open. Of the form language[-country] where language is the 2-letter code from ISO-639.
log-net-log	Enables saving net log events to a file. If a value is given, that value is used as the directory path and file name. If no value is given, the file is named netlog.json, and is placed in the user data directory.
long-animation-frame-timing	Provides detailed timing for long animation frames, which are frames exceeding the standard 16.67ms duration (60fps). This helps during debugging and performance analysis, to identify and optimize performance bottlenecks for animation-heavy applications.
msAbydos	Enables the "handwriting-to-text" experience.
msAbydosGestureSupport	Allows users to use gestures (such as the scratchout gesture) to delete text by using a pen. Valid only if the msAbydos flag is enabled.
msAbydosHandwritingAttr	Whether the "handwriting-to-text" experience is enabled for input elements at the DOM level. Valid only if the msAbydos flag is enabled.
msAllowAmbientAuthInPrivateWebView2	This flag is to be used along with the msSingleSignOnForInPrivateWebView2 browser flag, to enable single sign-on (SSO) with default credential flow or ambient authentication flow.
msEdgeDesignerUI	Enables the Designer Shoreline App. The Designer Shoreline App is not supported in WebView2.
msEdgeHubAppDesigner	Enables the Designer Shoreline App. The Designer Shoreline App is not supported in WebView2.
msEdgeDesignerDriverFix	Enables getting content and automatically showing the Designer feature. The Designer feature is not supported in WebView2.
msEdgeFluentOverlayScrollbar	Force-enables Fluent Overlay scrollbars, overriding whatever value kFluentScrollbar may hold at the moment.
msEdgeDevToolsWdpRemoteDebugging	Enables remote debugging. See Remote debugging WebView2 WinUI 2 (UWP) apps, Remotely debug Windows devices.
msEdgeWebViewApplyWebResourceRequestedFilterForOOPIFs	Makes the AddWebResourceRequestedFilter method (including overloads) also apply to out-of-process iframes. .NET: AddWebResourceRequestedFilter WinRT: AddWebResourceRequestedFilter Win32: AddWebResourceRequestedFilterWithRequestSourceKinds
msEnhancedTextContrast	Improves text contrast enhancement and gamma correction to match the quality and clarity of other native Windows applications. When this flag is used, font rendering respects user ClearType Tuner settings when applying text contrast enhancement and gamma correction.
msEnhancedTrackingPreventionEnabled	Enables native privacy protection features, such as blocking cookies and web requests that reside in domains that are known to be tracking domains.
msFloatyMode	Takes a true or false value. If true, enables the Floaty feature. If false, disables the Floaty feature. Use this flag to disable the Floaty feature, because WebView doesn't support browser retention experiments.
msFloatyShouldHonorIndiaHoldout	Takes a true or false value. If true, honors the India holdout group. If false, disables the Floaty feature that's enabled if the user is part of the India holdout group, because WebView doesn't support browser retention experiments.
msOverlayScrollbarWinStyle	Whether the users can change between overlay and non-overlay modes for Fluent scrollbars.
msPdfEnableAsPreview	This features enables the PDF viewer to launch with a minimal toolbar and in read-only preview mode.
msSingleSignOnForInPrivateWebView2	This flag enables the single sign-on (SSO) flow for InPrivate (Incognito) sessions of WebView2. Enables browser-based SSO in InPrivate (Incognito) mode.
msSingleSignOnOSForPrimaryAccountIsShared	Allows implicit sign-in to Microsoft webpages using any account, by using the information from the primary OS account.
msSmartScreenProtection	Makes SmartScreen protection available.
msUseSpellCheckCorrectionsCard	Causes a corrections card UI to be shown when the user clicks a misspelled word.
msWebView2BrowserHitTransparent	Causes mouse and keyboard events to pass through the WebView2 control to the underlying app, to allow the app to handle these events instead of the WebView2 control handling the events. When this flag is not enabled, the WebView2 control handles mouse and keyboard events; the events don't pass through to the underlying app. This flag allows testing how the app behaves when the WebView2 control doesn't intercept input events, for scenarios where the app needs to handle input events directly. This flag doesn't take a value. This flag might cause the app to crash or freeze.
msWebView2CancelInitialNavigation	Cancels the initial navigation in WebView2, to improve startup performance.
msWebView2CodeCache	Makes JavaScript resources that are loaded in a WebView2 app via SetVirtualHostNameToFolderMapping or add_WebResourceRequested eligible for bytecode caching, which should speed up the third and subsequent loads. This feature also enables bytecode caching for any other components that use the DevTools network interception mechanism to provide custom responses; see Custom management of network requests.
msWebView2EnableDownloadContentInWebResourceResponseReceived	Allows responses of navigations that become downloads to be available in WebResourceResponseReceived.
msWebView2TextureStream	Allows streaming captured or composed video frames to the WebView2 control, where JavaScript can render or otherwise interact with the frames via W3C standard DOM APIs, including the Video Embed element and MediaStream.
msWebView2EnableDraggableRegions	Takes a true or false value. If true, enables webpages within WebView2 make use of the app-region: drag\|nodrag CSS style, which causes elements with that style to behave like a titlebar. If false, or without this flag, the app-region: drag\|nodrag CSS style has no effect.
msWebView2NativeEventDispatch	Uses a native mojo connection to dispatch internal events, such as web messages to a renderer process.
msWebView2SimulateMemoryPressureWhenInactive	Simulates memory pressure for an inactive WebView.
msWebView2TreatAppSuspendAsDeviceSuspend	When all WebViews are suspended, makes WebView2 treat the app as if the device is suspended, and pauses all delayed tasks and timers.
no-proxy-server	Overrides any other proxy server flags that are passed.
net-log-capture-mode	Sets the granularity of events to capture in the network log. Valid values: Default, IncludeSensitive, Everything.
no-network-profile-warning	Causes the browser to warn if the UDF is on a network share. This flag is only supported on Windows; this flag is ignored on other platforms.
no-sandbox	Disables the sandbox for all process types that are normally sandboxed. Meant to be used as a browser-level flag for testing purposes only.
no-first-run	Skips First-Run tasks, regardless of whether it's actually the First Run, and skips displaying the What's New page. This flag is overridden by kForceFirstRun (for the First-Run Experience (FRE)) and by kForceWhatsNew (for displaying What's New). This flag doesn't drop the First Run sentinel, and thus doesn't prevent the First-Run experience from occurring the next time the Edge WebView browser is launched without this flag. This flag doesn't update the last What's New milestone, so doesn't prevent What's New from being displayed the next time the Edge WebView browser is launched without this flag.
PartitionedCookies	Enables sites to opt-in to having their cookies partitioned by the top-level site by using the Partitioned attribute. Partitioned cookies are only sent when the browser is on the same top-level site that it was on when the cookie was set.
proxy-auto-detect	Forces proxy auto-detection.
proxy-bypass-list	A list of hosts for which proxy settings are bypassed; the specified hosts then use direct connections instead. This flag is ignored unless --proxy-server is also specified. Multiple hosts can be supplied as a comma-separated list.
proxy-server	A proxy server that overrides system settings. This flag only affects HTTP and HTTPS requests.
remote-allow-origins	Enables web socket connections from the specified origins only. The * wildcard allows any origin.
remote-debugging-port	Enables remote debugging over HTTP on the specified port.
RendererAppContainer	Enables Renderer AppContainer.
Restart	Indicates that Microsoft Edge WebView2 browser process was restarted (such as after a flag change). Use this flag to ignore the launch when recording the Launch.Mode2 metric.
sdsm-state	The "Super Duper Secure Mode" state. Valid values: off, basic, balanced, strict.
SharedArrayBuffer	Indicates that a SharedArrayBuffer thread is present.
SpareRendererForSitePerProcess	Makes the Edge Webview spare renderer process try to always have a warm spare renderer process running for the most recently requested BrowserContext. This feature is only consulted in site-per-process mode.
ThirdPartyStoragePartitioning	Enables partitioning of third-party storage, such as IndexedDB or CacheStorage, by the top-level site, to reduce fingerprinting.
unsafely-treat-insecure-origin-as-secure	Treats given (insecure) origins as secure origins. Multiple origins can be specified, as a comma-separated list. For the definition of secure contexts, see Secure Contexts, including the section Is origin potentially trustworthy?. Example: --unsafely-treat-insecure-origin-as-secure=http://a.test,http://b.test.
use-fake-device-for-media-stream	Uses a fake device for Media Stream to replace an actual camera and microphone.
use-fake-ui-for-media-stream	Bypasses the media stream infobar, by selecting the default device for media streams (such as WebRTC). Works with --use-fake-device-for-media-stream. Prefer using --auto-accept-camera-and-microphone-capture instead, which doesn't interact with screen capture, such as capturing a browser tab.
use-system-proxy-resolver	Uses WinHttp to resolve proxies instead of using WebView2's normal proxy resolution logic. This flag is only supported in Windows.
user-agent	A string used to override the default user agent with a custom user agent.
user-data-migrated	Indicates that this process is the product of a relaunch following migration of user data.
UseBackgroundNativeThreadPool	Causes WebView2 ThreadPoolImpl to use a background ThreadGroup backed by a native thread pool implementation.
UseNativeThreadPool	Causes WebView2 ThreadPoolImpl to use a foreground ThreadGroup that's backed by a native thread pool implementation.
V8Maglev	Enables the Maglev compiler. This only sets the V8 flag when manually overridden; otherwise, it defers to whatever the V8 default is.

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See also

• Introduction to Microsoft Edge WebView2
• WebView2 API Reference - API Reference links for additional platforms and languages, such as WinRT/C++ (COM).