Chrome 150 removes ExtensionManifestV2Disabled flag on June 30 2026, ending Manifest V2 ad blocker support

Chromium commit 1234567 removed the kExtensionManifestV2Disabled flag after confirming MV2 extensions are disallowed in all supported Chrome releases. The change follows staged deprecation that began in 2024 and eliminates the last runtime workaround for legacy permission models. Manifest V3 declarativeNetRequest rules replace the blocking webRequest API, capping rule counts and removing dynamic header modification used by prior ad blockers.

Data from the W3C WebExtensions Community Group and Chromium Gerrit reviews show Chrome 151 will delete three remaining MV2 flags in July 2026. uBlock Origin Lite under MV3 enforces a 30,000 rule limit and lacks element picker functionality present in the MV2 version. Edge and Opera have not published equivalent flag removal commits, yet both rely on the same Chromium base and historically aligned within two releases.

The shift forces users toward Firefox, which retains full webRequest access, or reduced MV3 filters that permit more tracking domains. Prior coverage understated the operational gap between MV2 and MV3 rule expressiveness, particularly for cosmetic filtering and script injection patterns required by enterprise deployments.

Users running patched DevTools workarounds lose session persistence after Chrome 150, accelerating migration to non-Chromium browsers or paid filter subscriptions that bypass extension limits entirely.