Your favorite browser extensions might stop working soon, thanks to a big change Google is making to Chrome. This may severely limit the capabilities of "content blocker" extensions—including ad blockers and security extensions—that stop ads, trackers, and malware from loading in your browser.
It won't just affect Google Chrome; browsers like Microsoft Edge run on Chromium, which is the underlying code of Google Chrome. So what does this mean?
How Do Ad Blockers Work?
Ad blockers and other content blockers work by maintaining a list of requests to block before they load. If you visit a legitimate website that has been infected with malware, your content blocker can allow the legitimate website to load while blocking the connection to the infection before it can harm your device. See our guide on malicious websites and malvertising to learn how to spot them and protect yourself.
Additionally, most ad blockers have a feature called cosmetic filtering. After blocking the request to the ad server, websites still contain blank space where ads would normally be. To improve readability, cosmetic filtering removes those leftover spaces and condenses the website just before it finishes loading.
All browser extensions include a blueprint file called Manifest to tell the browser key information, like the permissions required. Manifest itself is an API, which stands for Application Programming Interface. Learn what an API is and how they work if you're not familiar. In short, it acts an interface between the extension and the browser, so they understand how to work together.
Support for version 1 was dropped completely in 2014, and version 2 is planned to end the same way. Version 3 is the version that may break content blockers, and changes are coming sooner rather than later.
What Will Manifest V3 Change?
Since January 2022, new extensions added to the Chrome Web Store have been required to use Manifest V3. In June 2023, extensions that use Manifest V2 will only be accessible if you have the link to them, before being removed completely in January 2024.
(Version 3 brings many changes; the ones we are focusing on are the limits imposed on content blockers.)
The lists of requests to block and cosmetic filtering we discussed earlier are also called rules. If your ad blocker has a list of malicious websites with 50,000 entries, it will set rules to block every website and check each request to see if there is a match.
Many ad blockers and security extensions have hundreds of thousands of rules, some give you the option to use millions. According to a blog post by AdGuard, who develop one of the most popular ad blockers with a Manifest V3 compatible extension, the imposed limits will be 30,000 rules per extension and 330,000 rules per user.
It goes on to explain how all filters except AdGuard's basic filter will be disabled, and you will be shown a message if this rule limit is reached. Even the basic filter can reach over 30,000 rules, and having multiple content blockers can put you over the 330,000 per user limit. Ad flickering also occurs as cosmetic filtering doesn't happen as quickly.
The problem isn't so much ad blockers and content blockers not being able to work with Manifest V3, it's how well they will work and how much they will be able to block.
Not Everybody Will Be Affected
Like we said at the beginning, this change will not only affect Google Chrome, but other Chromium browsers like Microsoft Edge. Mozilla Firefox will support Manifest V3 extensions, but not have this problem as rules will not have limits.
If you aren't using a content blocker, then you likely won't notice a difference with your existing extensions. If you are, you may be restricted to the amount of filters you can use and therefore ads you can block.
Google claims that Manifest V3 will improve security and performance overall, but some doubt the extent of these claims. Other ad blockers are likely to follow AdGuard in releasing Manifest V3 extensions, and ad blockers aren't going to disappear overnight.