Mozilla's upcoming mobile browser Firefox Fenix changes tabbed-browsing fundamentally

Martin Brinkmann
Mar 11, 2019
Firefox, Google Android

Mozilla is working on a new mobile web browser for Android called Firefox Fenix currently; that is the main reason why development for Firefox for Android slowed down in recent months.

Fenix is based on Android Components and GeckoView, and in active development at the time of writing. While it is likely that Firefox Fenix will replace Firefox for Android eventually, nothing appears to have been set in stone yet.

Note: The following information is based on mockups and development versions of Firefox Fenix. Functionality may change during development.

Firefox Fenix's tabbed browsing functionality

A core difference between Firefox Fenix and other mobile browsers such as Google Chrome or Firefox for Android, is that Fenix changes tabbed-browsing significantly.

All major mobile browsers supported tabbed-browsing. The functionality is more or less identical to how desktop browsers handle tabs. Users may open multiple tabs and open tabs are retained across browsing sessions.


Fenix supports browser tabs just like any other browser but changes tab management across sessions significantly.

Firefox Fenix stores open tabs in individual sessions; this happens automatically when the user exits the browser and does not reopen it shortly after exiting the application.

Means: the browser starts without open tabs from the last browsing session when the user opens the mobile browser at a later point in time.  Firefox Fenix users may save sessions manually at any time next to that.

mozilla fenix tabbed browsing

Sessions work differently from browsing sessions of desktop browsers. Fenix handles these sessions individually and gives users access to these tab sessions so that they may reopen sites they visited in the past.

The browser's homepage lists the current session and recent sessions opened in the browser. Fenix users may access these at any time from there to reopen sites that were open previously.

Fenix users may delete sessions, e.g. when they don't require access to them anymore. Sessions may also be archived for safekeeping.

fenix firefox

Mozilla plans to integrate session share functionality in Fenix next to that; this open may be used to send information about the current session using Android's Share functionality or linked devices or Firefox Sync.

fenix firefox 3

Closing Words

Mozilla's idea to change tab management in Firefox Fenix is certainly an interesting one. One benefit that comes out of it is that the browser won't use as much RAM as other browsers on mobile devices since tabs are only kept open during sessions but not across sessions.

Will there be an option to restore the classic behavior? We don't know the answer to that. It is certainly possible that some users will dislike the new method. Those who prefer to keep tabs open in the browser may find the new approach less useful as they'd have to reopen tabs frequently.  One way around this would be to allow users to lock tabs so that they remain open across sessions.

Now you: What is your take on this approach to tabbed browsing on mobile devices? (via Sören)

Mozilla's upcoming mobile browser Firefox Fenix changes tabbed-browsing fundamentally
Article Name
Mozilla's upcoming mobile browser Firefox Fenix changes tabbed-browsing fundamentally
A look at Firefox Fenix, a new browser by Mozilla for Android. The browser changes tabbed browsing significantly on Android devices.
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  1. Anonymous said on April 6, 2019 at 9:10 pm

    It will be nice if developers at first could fix existing issues at present Firefox, for example Firefox cannot open some web links what I am visiting on other we browsers for years and cannot open .pdf file in browser, even do not offer to download it, and then go further and continue develop a new browser.

    1. Anonymous said on April 8, 2019 at 5:34 pm

      What web links? You should report those to

  2. Zorro said on March 13, 2019 at 1:25 am

    If it does end up replacing Firefox for Android, I hope it will support add-ons and allow about:config-like customisation to e.g. make the browser 100% quiet for real.

  3. Anonymous said on March 12, 2019 at 12:14 pm

    So they integrate OneTab to browser! Revolution…

  4. Anonymous said on March 12, 2019 at 11:21 am

    Why can’t Mozilla just commit to updating a single browser? The monthly rebrandings just make things more confusing and invonvenient for users. Mozilla’s marketing department is pathetic, quite frankly.

    1. Anonymous said on March 12, 2019 at 5:19 pm

      This is eventually going to be an update to Firefox for Android.

      “Fenix” is an internal name, just like “Fennec” is the internal name of the current browser that’s branded as “Firefox for Android”.

  5. TG said on March 12, 2019 at 6:32 am

    I have been using fenix on android for about a month.
    And its a breeze to use.
    Takes a day or two to understand things have changed.
    But its way better to save sessions than loose tabs.
    There is no need of onetab/tab sessions like extensions.
    You could also use it for read later kind of scenario.

  6. Anonymous said on March 12, 2019 at 6:08 am

    I’ve been trying it out in the experimental builds. It kind of feels like the (Panorama) Tab Groups that Desktop Firefox had in earlier days.
    It’s obviously not quite as smooth to use, because you don’t get a big screen with thumbnails etc., but it’s still a lot less clunky than “sessions” makes it sound.

  7. fireattack said on March 12, 2019 at 12:22 am

    Sounds over-complicated for a mobile device to me.

  8. Greg said on March 11, 2019 at 10:44 pm

    i barely use firefox on the phone so i dont care, i only really use Chrome on android, its just like Mozilla’s Desktop Browser, it is just getting worse with each release

    1. AnorKnee Merce said on March 12, 2019 at 7:03 am

      @ Greg

      Chrome for Android does not allow extensions = cannot block ads from Google and coin-miners. Firefox for Android can.

      Yandex, based on Chromium, allows extensions. Bromite & Opera, based on Chromium, has a built-in adblocker.

      1. Greg said on March 13, 2019 at 1:21 am

        @ AnorKnee Merce

        but will this New firefox for Android allow extensions in it? it looks like a rather trimmed down firefox by the looks of it. im aware that Chrome for android doesnt allow extensions but as i posterd will this new firefox allow them still?

      2. AnorKnee Merce said on March 13, 2019 at 6:26 am

        @ Greg

        Firefox Fenix should be supporting extensions in its Final and transitionable version. …

        Otherwise, affected users will stay with Firefox Fennec or transition to Yandex.

      3. Greg said on March 13, 2019 at 9:56 am

        @AnorKnee Merce

        as Mozilla does tend to copy Google, i wouldnt hold ya breath that you’ll be able to use WebExtensions in this New Browser, i’ll just stick to the old current browser if that happens

      4. Kjm said on March 12, 2019 at 4:20 pm

        Also try Kiwi.

        Or if you have root on your phone you can install AdAway.

  9. XenoSilvano said on March 11, 2019 at 10:36 pm

    so many different version of Firefox on Android, why should I use Firefox Fenix over to Firefox for Android (Fennec) or Firefox Focus

    1. Anonymous said on March 12, 2019 at 5:41 am

      Well, the idea is that Fennec will be deprecated and Fenix will take its spot. So, somewhen, possibly this summer, a bigger update to Firefox for Android will just swap out the code bases.

      The main reason why they’re rebuilding Firefox for Android is that the integration of Gecko into the Android native toolkit wasn’t terribly clean when they did it.
      Now they’ve developed a cleaner integration, called “GeckoView”, which is also used in Focus (and the whole row of other Android browsers that they offer – yes, there’s even more).

      The most obvious difference will be that it will lag less. Even after the Quantum update and even if you enable the experimental WebRender, there’s some noticeable lag in Fennec when dragging your finger over the screen to scroll.
      Fenix, even in its current highly experimental state, is already much better at that.

      Another advantage will obviously be more unified codebases. Once this migration is completed, all of their Android browser will use these android-components as their foundation.

  10. Anonymous said on March 11, 2019 at 10:30 pm

    Ugly and dumbed down. How I miss late 2000s, early 2010s UIs.

  11. John Fenderson said on March 11, 2019 at 8:56 pm

    From a UI point of view, I think I’d rather have actual tabs over whatever that is in the mockups.

    “Firefox Fenix stores open tabs in individual sessions; this happens automatically when the user exits the browser and does not reopen it shortly after exiting the application.”

    From an operational point of view, I hope that there will be some way to disable this. I don’t want the browser to keep this kind of history at all — I want it to forget everything when I shut it down.

    1. Anonymous said on March 12, 2019 at 5:24 am

      If you actually mean *everything*, it does implement Private Browsing.

      1. John Fenderson said on March 12, 2019 at 4:06 pm

        @Anonymous: I don’t mean literally everything, I mean session history.

  12. Ray said on March 11, 2019 at 8:03 pm

    This resembles Firefox focus. It takes the functionality of Firefox Focus up a notch in that you can choose to save the sessions. By default, Firefox Focus does not remember the sessions or pushes you to delete the sessions.

  13. dood said on March 11, 2019 at 3:09 pm

    those arent tabs imo, dolphin browser has had real tab browsing on android from the beginning and it is the best android browser there is for that reason imo.

    1. Weilan said on March 12, 2019 at 8:46 am

      No, Dolphin is not the best browser. The best browser on Android is Firefox and the only reason for that is because I can install extensions like:

      – uBlock Origin
      – Popup Blocker (Strict)
      – Privacy Badger
      – User Agent Switcher

      and thus, Firefox becomes THE ONLY browser on Android that effectively and completely blocks all ads and popups EVERYWHERE.

      Can Dolphin do that? I don’t think so?

      Can the rest of the browsers do that? They are certainly trying, but none have as good ad-blocking, popup blocking and tracking blocking capabilities as Firefox… therefore all browsers that aren’t Firefox for Android are completely useless.

      The only disadvantage for Firefox is that it loads pages a lot slower than other browsers and if you don’t install an User Agent Switcher (a very specific one with a brown icon and change it to mask as Chrome on Android, Google Search will look like garbage to you.

      1. dood said on March 13, 2019 at 5:57 pm

        forgot to say *with adaway*

        true firefox allows extensions which is very good but with adaway I dont need any.

        root + adaway + dolphin is my go to, I much prefer the ui and everything dolphin than firefox, on mobile that is.

      2. Denn said on March 12, 2019 at 10:12 pm

        “Can the rest of the browsers do that? ” Yes. Yandex Browser

      3. Weilan said on March 12, 2019 at 11:37 pm


        I’ve tried it, it can’t block all ads and all popups.

        Go to: and try to watch a few episodes of any given show. I bet pretty soon you will run into ads and rogue popups.

      4. Weilan said on March 13, 2019 at 9:49 am


        I take my words back. Yandex has definitely come a long way – on both Android and PC.

        Something I previously deemed impossible, Yandex have achieved it – they allow you to install extensions from the Chrome Web Store on ANDROID! I can have my favorite extensions on Android on a browser that’s now as slow as Firefox.

        I just tried it on PC too – it feels a lot better than Chrome.

        I think I will be using it from now on.

      5. Tamris said on March 12, 2019 at 12:36 pm

        >The best browser on Android is Firefox

        If only it wasn’t so goddamn slow.

      6. Anonymous said on March 13, 2019 at 4:47 am


        That’s exactly what Fenix is going to fix. Even the experimental builds are already much smoother.

      7. John Fenderson said on March 12, 2019 at 4:04 pm


        I agree, the performance of Firefox on Android renders it unusable for me.. That’s pretty much the only thing that keeps me from using it. They’re working on it, though, so I have some hope that it will become usable for me at some point. We’ll see.

      8. AnorKnee Merce said on March 12, 2019 at 12:58 pm

        @ Tamris

        On my Android 8.0 tablet with an Octa-core chip, 3GB RAM and 32GB ROM storage, Firefox for Android is not damn slow but quite fast.
        ……. Of course, the initial opening of the browser, a new website or a new page is not very fast = takes seconds – same for any other browser.

        What are your hardware specs and Android version.?

      9. odin said on March 12, 2019 at 10:41 am

        The time it costs to change your user agent is better spend changing your search engine to ddg or startpage.

      10. Weilan said on March 12, 2019 at 4:40 pm


        believe me, I’ve tried. But sadly Google Search still provides the most relevant results.

        Whenever I tried to use a different search engine, I’ve spent twice or thrice as much time looking for what I want, whereas in Google Search, I find it almost instantaneously.

    2. nealis said on March 12, 2019 at 12:33 am

      Dolphin has been caught spying on its users from time to time. Everytime they give some excuse, but then years later we find out they do it again.

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