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SDK 1.0.4015-prerelease, for Runtime 149 (May 11, 2026)

Release notes for Microsoft Edge WebView2 Prerelease SDK, release date: May 11, 2026.

NuGet package for WebView2 SDK 1.0.4015-prerelease

For full API compatibility, this Prerelease version of the WebView2 SDK requires the WebView2 Runtime that ships with Microsoft Edge version 149.0.4015.0 or later; see Runtime 149.0.4022.49 (Jun. 11, 2026).

Breaking change: EnhancedSecurityModeLevel replaced by EnhancedSecurityModeState

The CoreWebView2Profile.EnhancedSecurityModeLevel property and the CoreWebView2EnhancedSecurityModeLevel enum are deprecated and will be removed in a future release. Replace all usage of these APIs in your WebView2 application, as follows.

The old property, CoreWebView2Profile.EnhancedSecurityModeLevel, controlled whether Enhanced Security Mode (ESM) is enabled or disabled for all WebView2 instances associated with a profile. This property has been renamed to EnhancedSecurityModeState, to more clearly communicate the state of Enhanced Security Mode.

Before this change: The CoreWebView2Profile.EnhancedSecurityModeLevel property used the CoreWebView2EnhancedSecurityModeLevel enum with values Off and Strict.

After this change: The CoreWebView2Profile.EnhancedSecurityModeState property uses the CoreWebView2EnhancedSecurityModeState enum with values Disabled and Enabled:

  • CoreWebView2EnhancedSecurityModeState.Disabled — Enhanced Security Mode is disabled.

    • Replaces CoreWebView2EnhancedSecurityModeLevel.Off.

  • CoreWebView2EnhancedSecurityModeState.Enabled — Enhanced Security Mode is enabled.

    • Disables JavaScript Just-in-Time (JIT) compilation.
    • Enables additional operating system protections.
    • Replaces CoreWebView2EnhancedSecurityModeLevel.Strict.

See also:

Experimental APIs (Phase 1: Experimental in Prerelease)

The following APIs are in Phase 1: Experimental in Prerelease, and have been added in this Prerelease SDK.

Enhanced security mode state

The EnhancedSecurityModeState property on CoreWebView2Profile controls whether Enhanced Security Mode (ESM) is enabled or disabled for all WebView2 instances that are associated with a profile.

When enabled, Enhanced Security Mode disables JavaScript Just-in-Time (JIT) compilation and enables additional operating system protections, reducing the attack surface, at the cost of some JavaScript performance.

The default value is Disabled. Changes apply immediately to new navigations; existing pages require a reload.

This setting does not persist, and resets when the profile is destroyed and recreated.

Promotions to Phase 2 (Stable in Prerelease)

The following APIs have been promoted from Phase 1: Experimental in Prerelease, to Phase 2: Stable in Prerelease, and are included in this Prerelease SDK.

Enable background processing and offline support (WebView2 Worker APIs)

The WebView2 Worker APIs allow host applications to interact with Web Workers to offload tasks from the main thread, improve responsiveness, and support background operations. These Web Workers include Dedicated Workers, Shared Workers, and Service Workers.

These APIs provide:

  • Lifecycle Events: Monitor creation and destruction of workers.
  • Messaging Interfaces: Communicate with workers using PostMessage and WebMessageReceived; specifically:
    • CoreWebView2ServiceWorker.PostWebMessageAsJson
    • CoreWebView2ServiceWorker.PostWebMessageAsString
    • CoreWebView2DedicatedWorker.PostWebMessageAsJson
    • CoreWebView2DedicatedWorker.PostWebMessageAsString
    • CoreWebView2ServiceWorker.WebMessageReceived
    • CoreWebView2DedicatedWorker.WebMessageReceived
    • chrome.webview.postMessage
    • Not: chrome.webview.postMessageWithAdditionalObjects
  • Worker Management: Query and retrieve worker registrations and instances.

Previous phase: Enable background processing and offline support (WebView2 Worker APIs) in Prerelease SDK 1.0.3415-prerelease, for Runtime 140 (Jul. 14, 2025).

See also

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