Google’s suggested Chrome changes disable some ad blockers

Raymond Hill, also known as Gorhill on the web, argues that Google’s proposed changes to the Chrome Extensions platform mean that the ad blockers he developed uBlock Origin and uMatrix can no longer continue to exist.

On Chromium’s bug tracker, Hill notes that Google’s proposed changes mean, among other things, that extensions are no longer allowed to use the webRequest API in “block mode.” This api can then only be used to observe things. Adblockers and other content-blocking extensions are only allowed to use the declarativeNetRequest API if the draft changes are actually implemented.

This declarativeNetRequest API uses an algorithm and filtering system that Hill claims is similar to that of Adblock Plus. He describes this ad blocker as ‘quite limited’, partly because it has a limit of 30,000 filters. That’s less than the 42,000 filters on EasyList’s list.

Hill’s ad blockers uBlock Origin and uMatrix use a different algorithm and have components that are incompatible with the declarativeNetRequest API. He also states that the api makes it impossible to come up with innovative filter engine designs, because the api is only based on the Adblock Plus system. Hill believes that this may make the designation user agent no longer applicable to Chromium.

Implementing the change in this way would increase the speed at which web pages load in Chrome, as extensions can only use the webRequest API to ‘watch’. Chrome no longer has to wait to load a page until the extension has weighed what should or should not be blocked. With the declarativeNetRequest API, the adblockers have to tell Chrome what to block, after which Chrome handles the blocking without waiting for adblockers to handle it.

Google says the proposed changes in the form of setting the declarativeNetRequest API are intended to increase performance, improve security, and ensure better privacy protection. The choice for adblockers to work in line with the Adblock Plus system may also be related to a 2015 Financial Times report in which the business newspaper claimed that Google and Microsoft paid Adblock Plus to whitelist ads.