During the Chrome Dev Summit, Google has formally included Manifest V3 in Chrome 88 Beta, allowing extension developers to test the changes to ad blocking, performance, and privacy.

Nearly two years ago, Google first took the wraps off of the next major revision of Chrome’s extension manifest, a specification for what Chrome extensions can do and how they can do it. Being the third version, it’s been dubbed “Manifest V3,” and it’s the first major revision to the spec since Manifest V2 launched in 2012.

When first proposed, Manifest V3 was a source of significant controversy, as it aimed to deprecate the blocking capabilities of the webRequest API, used by ad blockers like uBlock Origin and Ghostery. These capabilities offered extensions in-depth information about your web traffic and in Google’s words gave extensions “access to potentially sensitive user data.”

In the time since then, the Chrome team has taken some feedback from the extension developer community about the changes included with Manifest V3. One thing Google is strongly emphasizing is that ad blockers are welcomed in the Chrome extension ecosystem, but they’ll now need to use the new declarativeNetRequest API, which is less invasive to privacy. Google has even been working with the developers of AdBlock Plus on ensuring ad blockers continue to work with Chrome’s Manifest V3.

We’ve been very pleased with the close collaboration established between Google’s Chrome Extensions Team and our own engineering team to ensure that ad-blocking extensions will still be available after Manifest V3 takes effect.

— Sofia Lindberg, Tech Lead, eyeo (Adblock Plus)

One critique of declarativeNetRequest as it existed is that it only supported a maximum of 30,000 rules, while EasyList, one of the most popular sets of ad blocking rules, has over 60,000 rules. While Chrome 88 will still only allow 30,000 rules across all extensions, Google says that limit is set to expand to 300,000 in time for Chrome 89.

Elsewhere on the privacy front, Manifest V3 also allows people to have more fine-grained control over the websites a Chrome extension is allowed to have access to.

Another of Google’s core tenets of Manifest V3 is security, with the biggest change being that Chrome extensions can no longer run remote code. One advantage of this change is that it will be easier to audit the security and safety of extensions submitted to the Chrome Web Store, meaning the approval process should be much faster.

However, the flip side of that security change is that Chrome extensions like Tampermonkey that enable “user scripts” will not be able to exist in Manifest V3 as we know them today. According to Google, these extensions will need to make changes to comply with Manifest V3, and they’re specifically in talks with the developers of Tampermonkey and other extensions to find a solution to safely enable things like user scripts.

On the performance side of things, Chrome is looking to make extensions much less resource-heavy by allowing service workers to handle background tasks and event handling. Previously, this required a full “background page” to be quietly open, similar to having an extra tab open in your browser, adding to the amount of RAM Chrome uses.

All these Manifest V3 changes and more are now available to extension developers with the launch of Chrome 88 Beta, and the Chrome Web Store will begin accepting Manifest V3 extensions when Chrome 88 officially launches in January. Thankfully for those who use extensions that can’t currently be ported over, Manifest V2 extensions will continue to work for at least a year after Chrome 88 launches. In the meantime, Google will continue to take developer feedback, particularly from the public Chromium extension developers Google Group.

As Manifest V3 directly affects Chromium, other browsers that are compatible with Chrome’s extensions will also be affected by the changes of Manifest V3. For example, Microsoft has already announced that Edge will also be adopting the Manifest V3 changes.

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