A major technical transformation is unfolding in the web browser ecosystem, one that will permanently change the principles of working with add-ons. American tech giant Google has moved to the final stage of liquidating the Manifest V2 (MV2) platform in the Chrome browser. In the upcoming Chrome 151 update, Chromium developers will completely remove the system code supporting old extensions, blocking any remaining bypass methods, including corporate policies and hidden flags.

This step puts at risk the operation of popular ad-blocking and privacy protection tools that have relied on MV2 architecture for decades. However, against the backdrop of these changes, Brave Software has introduced its own compensatory mechanism designed to save users from losing functionality.

Technical Audit: Why Google is Removing MV2

Google justifies the transition to the new Manifest V3 (MV3) specification based on information security and power consumption optimization. The key difference lies in the architecture of access to network traffic. The MV2 standard provided extensions with the webRequest API, allowing third-party software to intercept, analyze, and modify all incoming and outgoing user traffic in real time.

In the new MV3 model, traffic management is delegated directly to the browser core. Extensions now interact through the declarativeNetRequest interface. This imposes strict technical limitations that are critical for dynamic filtering tools:

  • Rule Limit: While the number of filtering rules in MV2 was not limited at the system level, in MV3 this limit ranges from 30,000 to 40,000 rules per extension.
  • uBlock Origin Vulnerability: The full version of uBlock Origin, which uses over 300,000 rules, cannot operate within MV3 without significant functional cuts (the Lite version is required).
  • Fate in the Store: According to the official schedule, by August 31, 2026, all MV2-compatible products will be forcibly removed from the Chrome Web Store.

Although basic MV2 blocking was initiated earlier, advanced users maintained tool functionality using command-line flags (e.g., `--enable-features=AllowLegacyMV2Extensions`). In Chrome 151, these workarounds are deactivated without the possibility of restoration at the operating system registry level.

Brave's Countermove: Automatic Migration

Against the backdrop of infrastructural changes, independent developers are forced to form separate approaches to preserving privacy. Brave Software has implemented an automatic migration script (brave-core #37500) in browser version 1.92 and above.

The system now detects deactivated MV2 extensions from the Chrome Web Store, reserves user configurations, and automatically replaces them with similar versions hosted on Brave's own independent servers. At the current stage, native support for four critically important tools has been confirmed:

  • uBlock Origin
  • AdGuard AdBlocker
  • NoScript
  • uMatrix

Meanwhile, the native Brave Shields blocker operates at the level of the basic C++ engine, completely bypassing MV3 specification limitations.

The Fate of Alternatives: Firefox, Edge, and Opera

The Mozilla engineering team has confirmed a course of indefinite long-term support for Manifest V2 in the Firefox architecture. Developers are retaining the webRequest API as a standard system component, allowing the use of the original uBlock Origin without reducing filter bases.

The situation with Microsoft Edge and Opera browsers is different. Since they operate on the common Chromium branch, the liquidation of MV2 code in Google's repositories will lead to the automatic cessation of support for old extensions in these products in the near future. To preserve functionality, developers will have to deploy their own expensive forks of the network stack.

According to the technical regulations of the W3C consortium, web standard specifications are advisory in nature. However, the dominant position of the Chromium engine, which occupies more than 65% of the global desktop browser market, effectively turns Manifest V3 rules into a mandatory industry standard for independent software developers.