Manifest V3 extensions come to Chrome: here’s how they reduce the effectiveness of ad blockers


Almost two years ago, we discussed on this page a series of changes that Google was considering implementing in Chromium that could get rid of ad blockers (uBlock Origin, AdGuard, etc) as we knew them. It was the famous’ Manifest V3‘, in reference to the new format of the’ manifest ‘file that is packaged with each browser extension.

The controversy ended up fading over timeIts implementation seemed then something “long term”, and Google itself – which promised that the change only sought to improve the privacy, security and performance of the extensions – temporarily deactivated the criticism by promising indeterminate changes in the proposal.

But nevertheless, We are now two weeks away from January 2022 and, with this, that all new extensions that are incorporated into the Chrome Web Store have to adapt to the new manifest format.

What does all this mean to the user?

And yes, as we already said, these changes will end up coming months later to the pre-existing extensions, which they will cease to be able to be updated, first, and to function, later, if they are not added to the new format. So, let’s review, what does this mean for the user?

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Manifest V3 fundamentally assumes that Google will stop giving extensions access to a fundamental API for the operation of ad blockers (webRequest), in favor of another that will limit the effectiveness of these: declarativeNetRequest, which qualify as “more secure” and deny that it affects the functionality of the browser.

Only this is not true, because with declarativeNetRequest the extensions can no longer observe and filter the browser traffic and they go on to leave the filtering task in the hands of the browser, to which they limit themselves to communicating lists of rules.

The problem is that Manifest V3 also imposes a limitation on the number of rules that each extension can incorporate. DThe limit was originally set at 30,000 rules And, although Google later put its extension to 150,000 on the table, nothing more has been heard on that matter.

And it is something very relevant, since the standard configuration of uBlock Origin already makes use of 90,000 rules, and the full AdGuard configuration can easily exceed 150,000.

Furthermore, any slight change to these rules cannot be incorporated autonomously by each extension as they do now: they will be forced to do so as an update of the extension itself … updates Google would have the power to reject if the new rules include filtering of ads from its own platforms advertisements (AdSense, YouTube, etc).

UBlock Origin developer has already announced its refusal to launch a new extension whose filtering capacity is less than the current one (which means that it will no longer be usable when Manifest V2 extensions are excluded from the extension store) …

… And has already encouraged users to switch to Mozilla Firefox, whose managers have announced that, although they will adopt a format compatible with Manifest V3 to guarantee compatibility between extensions, will retain access to the webRequest API until there is an equally functional alternative.

AdGuard, for its part, has announced that it will join the new Manifest format, but that they will try to design its extension in such a way that the loss of filtering functionality is the least possible; in addition, recommend the use of their payment tools, as they operate at the operating system level and not the browser.

No security, no privacy, no performance – just conflict of interest

It is true that Google can rely on the fact that previous initiatives to tackle the problem of malicious extensions, based on the verification of its operation at the time of registration in your Chrome Web Store, have not proven to be of much use, and that is what has led to their decision to “cut their losses” and limit the scope of their access to the browser itself.

For the Electronic Frontier Foundation, however, there is much more behind Google’s decisions, starting with a clear conflict of interest generated by the fact that the company owns both the predominant web browser and the largest online ad network.

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The same conflict, in the eyes of the EFF, that drives other controversial Google measures such as FLoC and Privacy Sandbox:

“Considering that Google has been the world’s largest advertising company for years, these new limitations are paternalistic and downright creepy.”

“Google’s efforts to limit access [al tráfico del navegador por parte de las extensiones] they are concerning, especially considering that Google has trackers installed on 75% of the 1 million most visited websites. “

The EFF recalls that the changes introduced they hardly improve safety of users: that webRequest does not allow extensions to interfere with browser traffic it does not mean that they cannot continue to read certain data once loaded and get them to a third party.

“As for Chrome’s other justification for implementing Manifest V3, performance, a 2020 study by researchers at Princeton and Chicago Universities revealed that privacy extensions, the same ones that will now be hampered, actually improve performance. browser performance “.

And what are the rest of the browsers going to do?

Right now you will be thinking “But, at the After all, Google Chrome is not the only web browser in the world, truth? Aren’t we still able to turn to others to avoid Google’s arbitrariness? “Yes, that’s true (we’ve already talked about the solution proposed by Firefox above, in fact), but:

  • Google Chrome is the most used browser (and by far), which limits the scope of extensions that stay out of the Chrome Web Store.

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  • Google plans to implement Manifest V3 not only in Chrome, also in Chromium? the base on which most of the rest of browsers are developed: Microsoft Edge, Brave, Opera and Vivaldi.

  • The last three have already announced that they will make changes to preserve the privacy and ad-blocking features of Manifest V2. But none of them have their own extension download website.

  • Microsoft Edge does have its own store (which could prevent, for example, the rejection of extensions that block Google advertising), but as far as we know for now Microsoft has no plans to counteract the limitations imposed by Google on access to webRequest.


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