PSA: Chrome 150 removes key MV2 flag for uBlock Origin, Chrome 151 locks down the rest
Google Chrome is methodically dismantling support for Manifest V2 (MV2), the older extension framework that powers widely used tools like uBlock Origin. Chrome 150 removes a critical flag that kept MV2 alive, and Chrome 151 is set to eliminate most remaining workarounds for everyday users.
What Is Manifest V2, and Why Does It Matter?
Manifest V2 is the older technical standard governing how browser extensions interact with Chrome. It allows extensions like uBlock Origin to use a powerful API called `blockingWebRequest`, which intercepts and filters web traffic in real time. That capability is central to how uBlock Origin blocks ads and trackers so effectively. Google’s newer standard, Manifest V3 (MV3), restricts that same API, which critics argue weakens ad-blocking performance.
What Chrome 150 Breaks
A GitHub issue from the Chromium-for-Windows-7-REWORK project first flagged the change. Chrome 150 removes the `ExtensionManifestV2Disabled` flag, which was part of a command-line workaround users relied on to keep MV2 extensions running. Reports in Reddit’s r/uBlockOrigin confirm that updating to Chrome 150 caused classic uBlock Origin and other MV2 extensions to switch off automatically.
Previously, users could paste a specific command-line combination — `–disable-features=ExtensionManifestV2Unsupported, ExtensionManifestV2Disabled` — to restore MV2 functionality. That path no longer works in Chrome 150.
A limited workaround still exists in version 150. Some users report that disabling the `ExtensionManifestV2Unsupported` flag, then visiting the Extensions page and acknowledging a warning banner, can re-enable MV2 extensions. One user demonstrated that editing a disabled HTML attribute through Chrome’s built-in DevTools — developer tools that allow inspection of a page’s underlying code — could unfreeze the toggle and trigger a re-enable prompt. It works, but it is fragile and cumbersome.
What Chrome 151 Removes
Chrome 151 goes further. It removes the `ExtensionManifestV2Unsupported` flag, the `ExtensionManifestV2Availability` flag, and is expected to remove `AllowLegacyMV2Extensions` as well. Reports from r/chrome and the Chromium fork issue tracker confirm that from build 151.0.7874.0, the flag-based workarounds “no longer work” under normal conditions.
A W3C WebExtensions community note characterized Chrome 149 as the last version with full MV2 support on standard installs, framing 150 and 151 as the final steps in that phase-out.
Who Still Has Options
Chromium forks and advanced patching. Some Chromium-based forks retain an internal switch called `g_allow_mv2_for_testing`. Setting it to `true` restores MV2 support without any flags, even for Chrome Web Store installs accessed through direct links. One developer used WinDbg, a low-level Windows debugging tool, to toggle that Switch in Chrome Canary. A project called chrome_plus injects a DLL — a dynamic-link library, a type of shared code file — to perform similar in-memory patching on Chrome 151. These approaches are strictly for technical users comfortable with reverse engineering.
Enterprise and Education builds. The WebExtensions PSA notes that Chrome 151 drops MV2 only in “consumer install modes.” Enterprise and Education deployments retain MV2 support with blocking webRequest for now. Some technically inclined users have also found ways to configure their browsers to appear as enterprise installs, preserving MV2 access in the process.
The Practical Bottom Line
For most users, Chrome 150 is the last version where a combination of flags and basic UI steps can revive MV2 extensions. Chrome 151 effectively ends that era for standard installs, leaving only forked browsers, deep system patching, or enterprise configurations as viable paths forward. Users who depend on classic uBlock Origin should begin evaluating alternatives now, including the MV3-compatible version of uBlock Origin or other privacy-focused browsers that have committed to maintaining MV2 support.
