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Google has been in a tough tug-of-war with ad blockers for many years. Its main revenue source is online ads, but ads can be annoying, so many people block them, and this blocking extends to the company's own Chrome browser (download for iOS or Android), which is now the most dominant one in the world. And with Chrome's imminent "Manifest V3" update, those blocker add-ons now face some serious technical hurdles.

We've known about Manifest V3 for several months now, but one particular element of it has been getting a lot of new attention lately: If an ad blocker wants to check the source of an ad banner against a database of blocked sources, that list is restricted to no more than 30,000 entries. That may seem like a lot, but popular blockers can easily have hundreds of thousands of entries.

SEE: Google Chrome Review: How's the dominant king of web browsers holding up?

According to Google, web pages in Chrome tend to load more slowly if the browser has to consult a large ad blocking database every time it loads a page, so it plans to shut down the browser function that allows this behavior.

While this change may vex users who don't mind a short delay if it means fewer ads, Google also has to answer to millions of others around the world who will simply see a slow-loading page and potentially switch to another browser altogether.

Wither Mozilla Firefox?

Speaking of whom, its chief rival Mozilla Firefox (download for iOS or Android) does not have this database limitation -- and many of Firefox's browser extensions can be used on both the Android and desktop versions, whereas mobile Chrome does not allow any extensions. And while Firefox has been justifiably criticized in the past for sluggishness and instability, it's come quite a long way since the "Quantum" overhaul began in 2017.

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But with Microsoft recently announcing that its Edge browser (download for iOS or Android) will now use the same underpinnings as Chrome, including Google's add-on support system, Firefox's battle for market share isn't getting any easier.

By most estimations, such as that of StatCounter, Firefox is only on 1.6 percent of mobile devices worldwide, despite its recent performance and stability improvements. Chrome has about 57 percent of this market, while Safari trails at about 20 percent. In the United States, Firefox's share dips even further to 0.57 percent. Perhaps Google's latest move will tip the balance.


  • In a bid to improve page loading performance, an imminent update to the Google Chrome browser will severely impact the function of ad blockers; many of them may cease to function.
  • These blockers consult very long lists of links to determine if something should be blocked, and these databases can cause page loading delays in Chrome that could incentivize users to switch to another browser, such as rival Mozilla Firefox.

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Tom McNamara is a Senior Editor for CNET's Download.com. He mainly covers Windows, mobile and desktop security, games, Google, streaming services, and social media. Tom was also an editor at Maximum PC and IGN, and his work has appeared on CNET, PC Gamer, MSN.com, and Salon.com. He's also unreasonably proud that he's kept the same phone for more than two years.