Mozilla expects to launch extensions Manifest V3 support in Firefox in late 2022

Martin Brinkmann
May 19, 2022

Mozilla plans to introduce support for the extensions Manifest V3 in the organization's Firefox web browser in late 2022. Preview versions are already available in development editions of the web browser.

firefox enable manifest v3

While Mozilla plans to introduce support for Manifest V3 in Firefox, it won't remove support for APIs that are essential to privacy extensions. Content blockers and other privacy extensions will continue to function in Firefox as before, provided that developers continue to support them.

Manifest V3 defines APIs and the capabilities of browser extensions. Google announced the new version of the manifest in early 2019 and revealed that Chrome extensions would have to be updated eventually to remain available for users of the Chrome browser.

The initial version of the draft was discussed controversially. Developers voiced concern over some of the planned changes, as they would limit privacy-focused extensions such as content blockers from working properly. Google made some concessions to developers but continued its work on introducing the new capabilities and removing the old. The company landed Manifest V3 support in Chrome Canary 80 and in Chrome Beta 88.

Firefox extensions won't be limited by Manifest V3

Mozilla announced in 2019 that it would implement support for Manifest V3 in Firefox but would make adjustments to certain limitations. A new blog post on the Mozilla Add-ons Community blog sheds light on the adoption and the differences between Mozilla's and Google's implementation.

The decision to remove the blocking part of the WebRequest API and to replace it with the limiting declarativeNetRequest API was at the center of the controversy. Mozilla notes that the new API limits "capabilities of certain types of privacy extensions without adequate replacement".

Mozilla will keep the WebRequest API in Firefox to make sure that privacy extensions are not limited in providing the functionality they are designed for. The organization will implement the declarativeNetRequest API for compatibility reasons according to the blog post.

Mozilla will "continue to work with content blockers and other key consumers of this API to identify current and future alternatives where appropriate".

Firefox will also support Event Pages in Manifest V3 and introduce support for Service Workers in future releases.

Developer Preview

Developers may turn on the preview in the following way in current development editions of the browser:

  1. Load about:config in the web browser's address bar.
  2. Confirm that you will be careful.
  3. Search for extensions.manifestV3.enabled and set the preference to TRUE with a click on the toggle.
  4. Search for xpinstall.signatures.required and set the preference to FALSE.
  5. Restart Firefox.

Extensions may then be installed via about:debugging. Permanent installation of Manifest V3 extensions is possible in Nightly and Developer editions of the Firefox web browser. The implementation is not complete at the time of writing.

Now You: what is your take on Mozilla's decision?

Mozilla expects to launch extensions Manifest V3 support in Firefox in late 2022
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Mozilla expects to launch extensions Manifest V3 support in Firefox in late 2022
Mozilla plans to introduce support for the extensions Manifest V3 in the organization's Firefox web browser in late 2022.
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  1. zed said on May 26, 2022 at 11:30 am

    gorhill on declarativeNetRequest (“DNR”) API: “I can count over 420 filters currently in the default filterset which uses this feature, clearly a benefit to filter list maintainers. These filters would cease to exist in a DNR-based blocker. The core issue is the lid on innovation, which is key for content blocker to stay reliable. If the DNR API had been designed in 2014 according to the requirements of the time, content blockers would be awfully equipped to deal properly with the current landscape. The DNR API as designed now not only set back content blockers, but condemn content blockers to stagnate innovation-wise.”

  2. Mystique said on May 20, 2022 at 3:40 pm

    If google sees an opportunity to exploit its users they will almost certainly take it as long as it is not to obvious and sharp of a turn that it would damage the entire product and by that I mean all of its services. If they take careful and calculating steps that people will not notice then that is what they will do, its that tiny chipping away that google does best.

    A vast amount of Google and Google Chrome users are those that are casual users, it’s where Internet Explorer users went when that fell apart and once again that was another calculating move by Google to embed their toolbar into the IE which gave them a leg up when it came to transitioning. I do believe they deployed their tried and true method of foistware there too. Update Google Toolbar and install our chrome browser while you’re at it. The transition for those kinds of people was more orchestrated than they think.
    I’m not denying that there are not people that know what they are doing and consider themselves power users but yes the majority of users are a specific demographic of which many here are all aware of due to one capacity or another.
    Google is an established name that at one point we ourselves may have also trusted but have long since abandoned.

    Brave would be very wise to create and reveal their own extension store, in fact the more any third party browser splits away from Google the better.

    As far as Mozilla is concerned I see this as just a token of which will erode in good time, it may be another disaster like web-extensions.
    This could potentially be another opportunity for Mozilla and many others such as Brave to seize more marketshare but it won’t really bring in the casuals I referred to earlier because they know little as it is so we will have to wait and see how this pans out.

  3. wondering said on May 20, 2022 at 6:42 am

    What will happen to Brave, can it survive with such change?

    1. Neutrino said on May 20, 2022 at 11:49 am

      “What will happen to Brave, can it survive with such change?”

      Yes, they have their own blocker, which supports all the lists that UB is using, you just have to manually add them. It’s just that UB is much better at manually picking page elements to block, where the brave shield is not as refined.
      And, if the Brave people are smart, they’ll build their own extension store.

      The only real threat would be if google find a way to shove the mv3 crap in the chromium code itself where it’d not be possible to be ungoogled. Or somehow exploit their most used services to not work without. I’m just guessing here, but one thing is absolutely certain – Google, as the control freaks as they are, will never stop pushing their garbage.

  4. Greg said on May 20, 2022 at 3:36 am

    Mozilla will follow Google Chrome in 2023, Google OWNES Mozilla – Watch This Space

    1. ryuk said on May 21, 2022 at 12:47 pm

      Google all but owns the Web so everyone else has to adapt to the standards they dictate. That’s the sad state we’re in.

  5. Anonymous said on May 19, 2022 at 11:09 pm

    Firefox might just be back at the top soon once Google ruins Chromium with that Manifest v3 nonsense. The internet without adblocking is hell.

    1. m3city said on May 20, 2022 at 8:51 am

      I doubt. Most people don’t care. Unless browser becomes sluggish they won’t even think about changing it. I bet google will invest in chrome’s performance in case v3 hampered it, and in case of smarthphone browser – ppl would grab a new phone to mitigate the effect. If there was any. Being a FF user myself I don’t see any possibility to regain marketshare at all.

      1. Hitomi said on May 20, 2022 at 10:32 am

        You are wrong. They do care. Whenever I have randoms sit on my machine they ask me how “I made the internet look like this” and if I can do it on their browser as well. Most of them just are lazy and require spoonfeeding since they lack knowledge that is even available on the most normie sites like reddit and youtube.

        I am astonished how lazy some people are and rather tolerate the mental abuse of advertisers.

  6. Mark said on May 19, 2022 at 7:26 pm

    A small step in the right direction from Mozilla, but, they should restore completely the capabilities of legacy extensions.

    No surprise that what Chrome/Micro$oft are going after is filtering capabilities.

    I, for one want *NO* capitalist brainwashing AT ALL anywhere near my Firefox.

    1. Tom Hawack said on May 21, 2022 at 1:26 pm

      @Mark, do you think the Stasi was capitalist? Inquisition has always existed, independently of the political system. And is not ready to end. Be it as state police, private business. Information is gold, far more than gold, in all areas of life, and in all areas of life do we willingly or not leave a part of what defines our very own existence. The choice is : 1- paranoia, 2-surrender, 3- awareness. Maybe a 4- with disinformation, about ourselves, about divulged information, and that 4th option is unfortunately quite a fashion nowadays.

    2. Trey said on May 20, 2022 at 5:06 am

      “I, for one want *NO* capitalist brainwashing AT ALL anywhere near my Firefox.”

      Well Mark, I have some bad news for you…

  7. Brendan said on May 19, 2022 at 3:35 pm

    This is great news. Sounds like Mozilla has a solid plan

  8. can i have my money back said on May 19, 2022 at 2:34 pm

    Just wait until chrome extensions are restricted to web manifest v3 – keeping the old web declaration alive in code won’t mean jack shit when there’s nothing in the web extensions store to use it

    January 17, 2022: New Manifest V2 extensions will no longer be accepted by the Chrome Web Store. Developers may still push updates to existing Manifest V2 extensions, but no new Manifest V2 items may be submitted.

    January 2023: The Chrome browser will no longer run Manifest V2 extensions. Developers may no longer push updates to existing Manifest V2 extensions.

  9. Matti said on May 19, 2022 at 10:07 am

    Will wait for uBO developer to have a say on this. Ghacks comments (mine included) are irrelevant. Gorhill’s opinion is the only one that matters. If he has no complaints, it’s good enough for me.

    1. Dennis said on May 19, 2022 at 3:06 pm


    2. Anonymous said on May 19, 2022 at 2:19 pm

      lol… Gorhill hasn’t even started to develop manifestv3 uBlock, so what can he show about it? If you care about what he says like if he was the only person affected by this, then read but since he hasn’t started working on it, it is all speculation on his part, of course he has some important observations about some stuff, so it is good to read.

      But did you even try to stop being so obtuse and find other developers like Adguard team, who have already posted information about manifestv3, have been working on it and also know about it since it’s what their business is about?

      The article is not that old (September 2021), so it is less misinformation about manifestv3 with all the changes manifest v3 has been gone through.

      But the most important line is:
      “Will it become worse? Almost undeniably, but not by too much. The real victims in this transition are filter developers”

      So the thing is Filter lists are going to have a limit on the rules they can have, and that’s the main problem about it. For exmaple: right now Easylist has 66K rules, and the thing is many rules are already useless or obsolete and many of those rules are cosmetics not even ‘network’ ones so it is hard to calculate how it will get affected by manifestv3, but that’s what Adguard talks about since filter lists maintainers are the ones who have to have problems, but since the adblocking will keep working similar to today’s user needs, then I don’t see the drama about it for most people.

  10. Tom Hawack said on May 19, 2022 at 10:05 am

    Mozilla’s new blog post mentioned in the article is a must-read.

    My feeling is that slowly but surely Google constrictor, as the boa, is all in its long-term strategy aiming a full control of users’ surfing experience and data.

    Cross-browser compatibility constriction on a market dominated by Google : quoting Mozilla’s blog,

    “In 2018, Chrome announced Manifest v3, followed by Microsoft adopting Chromium as the base for the new Edge browser. This means that support for MV3, by virtue of the combined share of Chromium-based browsers, will be a de facto standard for browser extensions in the foreseeable future. ”

    A suffocated browser’s attempt to breath and let its users breath as well : quoting Mozilla’s blog,

    “Mozilla will maintain support for blocking WebRequest in MV3. To maximize compatibility with other browsers, we will also ship support for declarativeNetRequest.”

    I just wonder how long resistance will be possible.

    1. Yash said on May 19, 2022 at 8:00 pm

      I like how Mozilla is dealing with this Manifest V3 changes – Manifest V3 + declarativeNetRequest API. Developers will not lose anything and users will have what they want.

      Mozilla’s post can also be read as – there are way too many normies who don’t care what Google is doing. They don’t consider alternatives. They even reject alternatives. Anyway we will continue to do things our way as long as we can to have an alternative. But things are getting harder.

    2. Gerard said on May 19, 2022 at 5:02 pm

      I agree, the blog post is essential reading material.
      Google won’t stop until it fully controls the WWW. Perhaps it even wants to control the complete internet, so that for all practical purposes internet=Google and Google=internet. And perhaps it won’t stop there either.

  11. nuts said on May 19, 2022 at 9:41 am

    I hope FoxReplace still works.
    It’s a quick way to basic html modifications site wide.

    1. T. said on January 14, 2023 at 4:00 am

      Not sure if related, but it stopped working for me (several versions back I believe). :-/

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