One morning a friend messaged us: "Chrome says my ad blocker is no longer supported. Is my computer broken?" It was not. Chrome had finished moving browser extensions from an older system called Manifest V2 to a newer one called Manifest V3, and some extensions built for the old system were switched off.
If you saw that warning, this post explains what happened, why it matters for ad blockers in particular, and what your options are.
What a "manifest" is
Every browser extension includes a small file called a manifest. It tells the browser what the extension is, what it wants to access, and which browser features it uses. The "version" of the manifest is really the version of the extension platform: which rules extensions must follow.
Manifest V3 is the newer platform. Chrome announced it years ago and phased out Manifest V2 gradually through 2024 and 2025: first warnings, then disabling old extensions with an option to turn them back on, then removing that option. Today, Manifest V2 extensions do not run in stable Chrome.
What changed, in plain terms
Under Manifest V2, an ad blocker could look at every network request a web page made (every image, script and tracker) and decide, with its own code, whether to block it. That is powerful and flexible. It also means the extension sees everything you load, and a malicious extension could use the same power to spy on you or change pages.
Under Manifest V3, Chrome replaced that with a system called declarativeNetRequest. Instead of inspecting each request itself, the extension hands Chrome a list of rules ("block requests to this domain", "remove this part of the address"), and Chrome applies them. The extension never sees the requests.
The other big change: extensions can no longer run code downloaded from a server; all their code must ship inside the reviewed package.
Manifest V2 | Manifest V3 | |
|---|---|---|
How blocking works | Extension code inspects each request | Extension gives rules, the browser applies them |
Number of rules | Practically unlimited | Limited (generous, but capped) |
Updating filter lists | Anytime, from the server | Rule lists bundled with the extension, plus a smaller set of dynamic rules |
Privacy of browsing data | Extension can see every request | Extension does not see requests for blocking |
Remote code | Allowed in some cases | Not allowed |
Why Google says it made the change
Google's stated reasons are security, privacy and performance. Extensions with full access to every request have been abused for data theft and ad injection. Rule-based blocking runs inside the browser and does not slow pages down with extension code. Banning remote code makes extension review meaningful, because what is reviewed is what runs.
Why ad blocker makers were unhappy
The developers of advanced blockers, such as uBlock Origin, argued that rule limits and the loss of custom logic make blocking weaker. Advanced filters that depend on running code per request, or that react to how a page behaves, are hard or impossible to express as static rules. Filter lists also update less flexibly, which matters when advertisers change tactics quickly.
Critics also pointed out that Google earns most of its revenue from advertising, while Google says the rule limits were raised after feedback. Both things can be true: the change has real security benefits and real costs for blocking quality.
What actually happened to popular extensions
uBlock Origin (the Manifest V2 version) was disabled in Chrome. Its developer publishes uBlock Origin Lite, a Manifest V3 version with fewer features but solid default blocking.
AdGuard, Ghostery, Adblock Plus and others released Manifest V3 versions.
Most other extensions (password managers, translators, note tools) updated without users noticing.
For normal browsing with standard ad and tracker lists, a good Manifest V3 blocker still removes most ads. The difference shows up on sites with aggressive ad tricks and for users who wrote their own advanced filters.
Your options by browser
Chrome: install a Manifest V3 blocker such as uBlock Origin Lite or AdGuard. Enable the strongest filtering mode the extension offers; some ask for extra permission to work on all sites.
Firefox: Mozilla supports Manifest V3 but kept the old blocking ability, and said it continues to support Manifest V2 extensions. The full uBlock Origin still works in Firefox, on desktop and on Android.
Brave, Opera, Vivaldi: these have ad blocking built into the browser itself, so it is not limited by extension rules. Brave Shields in particular is strong by default.
Edge: follows Chrome's extension platform; use Manifest V3 blockers.
Safari: has always used a rule-based content blocker model, similar in spirit to Manifest V3. Blockers come from the App Store.
How to check what an extension uses
You do not need to read code to see if an extension is ready:
In Chrome, open the extensions page (type
chrome://extensionsin the address bar).Turn on Developer mode at the top right. Each extension card now shows extra details.
Extensions that Chrome has disabled for Manifest V2 show a warning on the card, with a link to find an alternative in the Chrome Web Store.
On the extension's store page, the "Updated" date tells you if the developer still maintains it. An extension not updated for years is a risk regardless of its manifest version.
If an extension you depend on was disabled and has no Manifest V3 version, search the store for an alternative from a well-known developer, or check whether the tool has a desktop app or a website that does the same job.
For companies and IT teams
Organisations that manage Chrome through policy had extra time for Manifest V2 extensions, but that exception has also ended. If your company uses an internal extension (for single sign-on, data loss prevention or internal tools), make sure it has been migrated and tested. Chrome Enterprise policies still let administrators force-install, allow or block extensions, and some enterprise-installed extensions keep additional capabilities that normal extensions do not have. Check the Chrome Enterprise documentation for what applies to your deployment.
A note on safety
Whatever you choose:
Install blockers only from the official browser store, and check the developer name. Fake "ad blocker" extensions that inject their own ads are common.
Avoid extensions that promise to "restore Manifest V2" in Chrome. There is no safe way to do that in stable Chrome, and such tools are a malware risk.
Fewer extensions is better. Each one is code running inside your browser.
Key takeaways
Manifest V3 is Chrome's newer extension platform; Manifest V2 extensions no longer run in stable Chrome.
Ad blockers now give Chrome a list of rules instead of inspecting traffic themselves, which is safer but less flexible.
Good Manifest V3 blockers still block most ads; the full uBlock Origin remains available in Firefox.
Browsers with built-in blocking (Brave, Opera, Vivaldi) are not affected by the extension limits.
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