Firefox has become the last major web browser that still fully supports uBlock Origin, the popular ad and tracker blocker, as Google’s overhaul of Chrome’s extension system continues to limit what the tool can do elsewhere. The shift, detailed in a report from PCWorld, means users who want the extension’s original, most powerful filtering capabilities are increasingly funneled toward Mozilla’s browser.
What changed with Manifest V3
The root of the split is Manifest V3, Google’s new framework for how browser extensions are built and what permissions they can use. Chrome began requiring extensions to migrate to Manifest V3 rules over the past two years, phasing out support for Manifest V2, the older standard that gave content-blocking tools like uBlock Origin broad, real-time access to network requests through the webRequest API.
Under Manifest V3, that capability is replaced by a more restricted API called declarativeNetRequest, which caps the number of filtering rules an extension can apply and limits how dynamically it can respond to new threats. Because of these constraints, uBlock Origin’s developer, Raymond Hill, built a separate, scaled-down version called uBlock Origin Lite for Chromium-based browsers. It blocks most conventional ads but lacks the deeper customization, dynamic filtering, and aggressive tracker-blocking that power users rely on in the full version.
Chrome, Edge, and other Chromium browsers follow suit
Because Microsoft Edge, Brave, Opera, and Vivaldi are all built on the Chromium engine that underlies Chrome, they inherit Google’s extension policies to varying degrees. Chrome has been actively disabling Manifest V2 extensions for most users, pushing them toward Manifest V3 alternatives. While some Chromium-based browsers have said they would try to preserve elements of the older system for longer, they are ultimately constrained by the same underlying platform Google controls, meaning full uBlock Origin support is being squeezed out across the board.
Why Firefox is different
Mozilla has taken a different path. Firefox has continued to support Manifest V2 alongside Manifest V3, and the company has said it does not plan to remove the older webRequest-based blocking capability that uBlock Origin depends on. That means Firefox users can still install the full, unmodified version of uBlock Origin, with all of its advanced filtering, custom rule lists, and dynamic blocking intact.
This has made Firefox something of a refuge for privacy-focused users and those who rely on aggressive ad blocking for reasons beyond convenience, including reducing exposure to malicious ads and invasive tracking scripts. Extension developers and privacy advocates have pointed to the gap as one of the clearest practical differences left between the major browsers.
What this means for everyday users
For most casual browsers, the difference may not be immediately obvious. uBlock Origin Lite still blocks the vast majority of standard display ads on Chrome, Edge, and other Chromium browsers. But the practical impact grows for users who depend on more sophisticated filtering, such as:
- Blocking ads embedded directly in video streams or that use evasive techniques to bypass simple rule sets
- Using large, frequently updated community filter lists that exceed the rule caps allowed under Manifest V3
- Blocking scripts and trackers dynamically based on real-time behavior rather than static rules
- Customizing filtering with advanced options like dynamic filtering by domain or script type
Users who rely on these features are increasingly likely to find Firefox, or Firefox-based browsers, as the only option that preserves them without workarounds.
Google’s stated reasoning
Google has defended Manifest V3 as a security and performance upgrade, arguing that the older webRequest API gave extensions too much unchecked access to browser traffic, which could be exploited by malicious add-ons. The company has said the new architecture reduces the risk of extensions intercepting or altering sensitive data without a user’s knowledge.
Critics, including Hill and many privacy researchers, counter that the changes disproportionately weaken legitimate ad and tracker blockers while doing little to stop bad actors, who can still find other ways to build harmful extensions. That tension has fueled ongoing debate over whether Manifest V3 genuinely improves security or primarily serves Google’s advertising business, given that Chrome is developed by a company that also runs the world’s largest online ad network.
Looking ahead
For now, the practical takeaway is straightforward: users who want the most complete, unrestricted ad-blocking experience have one clear browser to turn to. Whether other browser makers eventually find ways to restore fuller blocking capabilities within or alongside Manifest V3 remains uncertain, but as of this month, Firefox holds a distinct position as the last major holdout preserving uBlock Origin in its original form.
The split underscores a broader shift in how much control browser makers retain over the tools users install to manage their own privacy and browsing experience.
