A Major Shift in How Chrome Handles Extensions

Google has been rolling out Manifest V3 (MV3) — a new framework governing how browser extensions work in Chrome. While Google positioned the change as a security and performance improvement, critics in the privacy community argue it significantly weakens the ability of ad blockers to function effectively.

If you rely on extensions like uBlock Origin or similar tools, this change matters to you.

What Is Manifest V3?

Browser extensions are built using APIs defined by a "manifest" — essentially a rulebook that determines what an extension can and can't do. Manifest V2 (MV2) was the previous standard. Manifest V3 replaces it with a new set of rules that limit certain extension capabilities.

The most significant change for ad blockers: MV3 replaces the powerful webRequest API (which allowed extensions to intercept and modify network requests in real time) with a more limited declarativeNetRequest API.

Why Does This Weaken Ad Blocking?

The old webRequest API gave ad blockers full access to inspect every network request a page made, allowing them to block ads dynamically and apply complex filtering logic. The new declarativeNetRequest system requires extensions to pre-declare a list of rules — and caps how many rules they can have.

The practical impact:

  • Rule limits: MV3 imposes caps on the number of blocking rules an extension can use, limiting how comprehensive filter lists can be.
  • Less dynamic filtering: Advanced techniques like uBlock Origin's dynamic filtering become harder or impossible to implement.
  • Reduced cosmetic filtering: Hiding ad elements on pages (rather than just blocking their network requests) becomes more complex.

Google's Stated Reasons

Google argues that MV3 improves:

  • Privacy: Extensions can no longer read all your network traffic by default
  • Performance: Declarative rules are processed more efficiently by the browser
  • Security: Reduces the risk of malicious extensions

There is merit to some of these points. MV2 did give extensions very broad access. However, critics note that Google — which earns the vast majority of its revenue from advertising — has a clear financial incentive to limit ad blockers.

What Happened to uBlock Origin?

The developer of uBlock Origin (Raymond Hill, known as gorhill) has been vocal about MV3's limitations. On Chrome, uBlock Origin (MV2 version) has been deprecated. A scaled-back version called uBlock Origin Lite was released for MV3 compliance, but it lacks many features of the full version.

On Firefox, the full-featured uBlock Origin continues to work — Mozilla has committed to maintaining MV2 support and extended the webRequest API even in its own MV3 implementation.

What Should You Do?

Option 1: Switch to Firefox

Firefox is the most straightforward solution. It supports the full uBlock Origin and has committed to maintaining the APIs that make powerful ad blocking possible. Firefox also has strong built-in tracking protection.

Option 2: Use Brave Browser

Brave's built-in ad blocker operates at the browser level — not as a Chrome extension — so it's unaffected by MV3 extension limitations. It remains one of the most effective ad blockers available.

Option 3: Stay on Chrome with uBlock Origin Lite

If you need to stay on Chrome, uBlock Origin Lite is still better than nothing. It blocks most common ads, just without the advanced filtering features.

Option 4: Use a Network-Level Blocker

Tools like Pi-hole or AdGuard Home run on your local network and block ads at the DNS level — completely independent of browser extensions and unaffected by MV3.

The Bigger Picture

The MV3 transition is a reminder that browser vendors have enormous power over your privacy. Choosing a browser whose financial incentives align with your privacy interests — rather than with the ad industry — is one of the most important privacy decisions you can make.