What Is Manifest V3 and Why Chrome Is Forcing Extensions to Switch

Manifest V3 is the current version of the system Chrome extensions are built on. Every extension has a manifest file that tells Chrome what it is and what it may do, and the "version" sets the rules it has to follow. Chrome has now switched off extensions still built on the old Manifest V2.

What changed from Manifest V2

• Background work. V2 extensions could keep a background page running all the time. V3 uses service workers that start when needed and stop when idle, which saves memory but means extensions can't hold state in memory forever.
• Blocking web requests. In V2, an extension could inspect every network request and decide in code whether to block or change it. In V3, extensions mostly give Chrome a list of rules (the declarativeNetRequest system) and Chrome applies them. There are limits on how many rules an extension can use.
• No remote code. V3 extensions can't download and run code from the internet. All their code has to be in the package Google reviews.
• Tighter permissions and more modern code, such as promises in the extension APIs.

Why Google made the switch

Google says V3 improves security, privacy and performance. Banning remote code makes it harder for an extension to pass review and then change behavior. Rule-based blocking means an extension doesn't need to see every request you make to block ads.

Critics, including ad blocker developers and privacy groups, point out that V3 limits what ad blockers can do, and that Google earns most of its money from ads. Both points are true at once.

What it meant for ad blockers

The best-known casualty was uBlock Origin, which relied on V2's request blocking and no longer runs in Chrome. Its developer released uBlock Origin Lite for V3. It blocks most ads and trackers well, but has fewer advanced options and custom filters. Other big blockers, such as AdGuard and Ghostery, moved to V3 versions.

The timeline

V3 arrived in Chrome in 2020. Google began turning off V2 extensions for regular users in 2024 and finished in 2025, including the temporary option that let businesses keep them running. If an old extension now shows as no longer supported, it was never updated to V3.

Other browsers

• Edge and most other Chromium browsers followed Chrome's schedule.
• Firefox supports V3 but kept V2 and the older request-blocking API, so the full uBlock Origin still works there.
• Brave blocks ads in the browser itself, so its built-in blocking doesn't depend on extensions.

For extension developers

Moving to V3 usually means rewriting the background script as a service worker, replacing request blocking with rules, and bundling any remote code. Every Bushe.co extension is built on Manifest V3. If you need an extension built or migrated, see Chrome extension development.