Google considers move that would block ad blockers in Chromium

Technical change intended to improve browser security would bork ad blockers in Chrome, Opera and Vivaldi

Google is considering a technical change to its Chromium open source web browser project that would break ad blockers in Chrome, Opera and Vivaldi.

The move has been mooted in the ‘Manifest 3' document, which is intended to highlight upcoming development proposals. One of the proposals includes a suggestion to "strive to limit the blocking version of webRequest, potentially removing blocking options from most events". The makers of ad blockers, though, claim that this would effectively break their software.

Although the webRequest API will be maintained, it will be severely restricted in functionality, requiring ad blocking software to be rewritten or even re-architected. The document suggests that ad blocker developers could use the declarativeNetRequest API instead, but the developers claim that won't necessarily be a straightforward shift.

"The declarativeNetRequest API is no more than the implementation of one specific filtering engine, and a rather limited one," wrote one developer responding to the proposals.

The developer continued: "There are other features (which I understand are appreciated by many users) which can't be implemented with the declarativeNetRequest API. For example, the blocking of media elements that are larger than a set size, the disabling of JavaScript execution through the injection of CSP directives, the removal of outgoing Cookie headers…

"Extensions act on behalf of users, they add capabilities to a *user agent*, and deprecating the blocking ability of the webRequest API will essentially decrease the level of user agency in Chromium, to the benefit of web sites which obviously would be happy to have the last word in what resources their pages can fetch/execute/render."

Google claims that the move is being considered to improve security.

Google's argument is that declarativeNetRequest will enable Chrome to modify or redirect network requests, which will be used to speed the whole thing up. It's also more secure, in that nobody will be able to see those network requests. However, it will also take away the fundamental way in which adblockers identify and block adverts.

The only way non-Google browser makers will be able to avoid the coming break would be to fork the Chromium project, although that would require a large injection of labour given the support that Google puts behind Chromium.