Firefox 34 Find out what is new

Martin Brinkmann
Dec 1, 2014
Updated • Jan 12, 2015

Mozilla is rolling out updates for specific versions of the web browser. If you are running a non-stable build you may have already received updates last week as Mozilla postponed the release of the stable version and the ESR version by one week to get additional development time to stabilize development.

This means that stable users will receive the upgrade to version 34, Beta users to 35, Developer Edition (former Aurora) users to version 36, and Nightly users to 37.

In fact, some version have already been upgraded by Mozilla in the past but the stable update is definitely coming this week.

To find out which version and channel you are running type about:support in the browser's address bar and hit enter. You find the information listed under Application Basics there.

Firefox 34 Download

firefox 34 stable

Mozilla will make available the update to Firefox 34 in a bit. As always, it is already available on the official (and public) ftp server from where it can be downloaded.

Several third-party downloads sites are also hosting the Firefox 34 download already.

It is possible that Mozilla will push another version out to users if last minute changes demand it. It is best usually to wait for the official release announcement before the new version is downloaded.

Most users of the browser will receive the update via the built-in automatic update functionality but it will be made available on the official Mozilla website as well.

Firefox 34 Changes

Firefox 34 introduces several changes and improvements to the browser. The following paragraphs list the most important of them.

New Search Bar Behavior

firefox search beta

I have reviewed this when it landed in Firefox Beta. It changes Firefox's separate search form that is displayed by default in several ways.

Most notable is the display of other search providers installed in the browser so that you can run searches using them instead of the default search engine with just a click.

Mozilla added a search tab to Firefox's options which you can use to manage the search providers more comfortably in the browser.

firefox search preferences

You can change the default search engine there and select which search engines you want displayed as one-click options in the search form.

Firefox users who don't like the change can disable it in the following way:

  1. Type about:config in the browser's address bar and hit enter.
  2. Confirm you will be careful if the prompt appears.
  3. Search for and set it to false.

Note: This is currently only available in the US version of Firefox.

Firefox Hello


This is a new real-time communication feature of Firefox using WebRTC. It enables you to communicate with friends, family and colleagues using the browser and nothing else.

What you may find interesting about it is that it does not require the creation of an account to communicate with other users. You have to exchange a link then. Users who don't mind the creation of accounts can use their Firefox account to save contacts and other information so that they are always available right away in the browser without having to exchange links first.

Firefox Hello supports voice and video calls and requires no additional software or plugins.

Mozilla is rolling out the feature gradually. To get it right away, set the preference loop.throttled to false and restart Firefox. Hello should be available then,

Check out my full review of Firefox Hello here.

Theme switching in customize menu

firefox customize themes

If you switch themes regularly you may like the option to do so in the new customize menu.  You find five default "light" themes that Firefox ships with there that you can switch between.

You find installed Personas themes there as well so that you can switch between them. Please note that this does not include so-called complete themes in any way as they are not listed there at all.

It is still possible to enable, disable or uninstall themes in the add-ons manager.

Firefox is already running on Windows fix

firefox already running

Firefox is already running can come up when you try to open Firefox when a browser process is still running on the system. This can happen when the Firefox profile is locked for example and can be caused by Firefox running exit processes in the background before the process itself is terminated (say you have configured it to delete temporary data on exit for example).

From Firefox 34 on, Windows users receive a different message that they can use to close that Firefox process which terminates it on the system.

It is like you opening the Task Manager and killing the Firefox process manually, only faster.

I have reviewed the new feature here in detail.

Other Changes

  • Default search engine changed to Yandex for Belarusian, Kazakh, and Russian locales.
  • Disabled SSLv3.
  • Firefox signed by Apple OS X version 2 signature
  • HTTP/2 (draft14) and ALPN (Application-Layer Protocol Negotiation) implementation.
  • Proprietary window.crypto properties/functions re-enabled (to be removed in Firefox 35)
  • Wikipedia search is using https now (US-only).

Developer Changes


  • New Storage Inspector. This needs to be enabled in the Firefox Developer Tools (press F12) first before you can use it. Locate Storage in the options and check the box next to it to enable it. Additional information here.
  • WebIDE enabled by default. Shipped in Firefox 33 but was disabled by default. You can use it to run and debug Firefox OS apps. Additional information here.
  • Performance tool revamped Profiler interface and frame rate timeline.
  • jquery events visible in Page Inspector
  • console.table support
  • CSS Fonts Level 3 progress.
  • WebCrypto: RSA-OAEP, PBKDF2, AES-KW and ECDH support.
  • ECMAScript 6 Weak6.
  • JavaScript Template Strings.

Firefox 34 for Android

Firefox for Android and the desktop version of Firefox share improvements. This part of the review looks only at Android-specific changes.

Chromecast Mirror Tab support

firefox android mirrorcast

Firefox for Android users who also own a Chromecast can mirror tabs displayed in the mobile browser now. This is done by tapping on the menu button on the device and selecting Tools > Mirror Tab from the context menu that opens up.

All devices are displayed on the next screen and all that is left to do is pick one of them to start the mirroring process. To stop the process tap on the menu button again and select stop mirror from there.

  • Added support for Prefer:Safe HTTP Header - If parental controls are enabled, Firefox will send a Prefer:Safe header to every site and service that is visited using it. Sites that support the header may deliver different contents or restrict access to some contents.
  • Device Storage API for privileges apps enabled. Additional information here.
  • Public Key Pinning support enabled - This allows sites to specify certificate authorities on first connect. Firefox will then use these information on future connections to those sites.
  • Theme refresh
  • Redesigned first run experience
  • Fixed: mp4 videos on Android L
  • Unresolved: Flash and mp3 does not work on Android L.

Security updates / fixes

Security updates are published after the release of Firefox. We will add those once they become available.

  • MSFA-2014-89 Bad casting from the BasicThebesLayer to BasicContainerLayer
  • MSFA-2014-88 Buffer overflow while parsing media content
  • MSFA-2014-87 Use-after-free during HTML5 parsing
  • MSFA-2014-86 CSP leaks redirect data via violation reports
  • MSFA-2014-85 XMLHttpRequest crashes with some input streams
  • MSFA-2014-84 XBL bindings accessible via improper CSS declarations
  • MSFA-2014-83 Miscellaneous memory safety hazards (rv:34.0 / rv:31.3)

Additional information / sources

Now Read: Firefox Release Schedule

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Software Name
Firefox 34
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  1. Anon E Mous said on February 28, 2015 at 11:06 pm

    With correction (2nd submission attempt):

    tldr; : Open source alternatives that can do the same thing as Firefox Hello (that is, communicate using the open WebRTC standard), but without the onerous legal terms required by TokBox and Mozilla (makers of Firefox), either will become available, or already are. It is wisest to regard Firefox Hello as a bug or malware, and to disable it.

    Firefox Hello uses WebRTC, which is an API, or standard, defined by the W3C consortium. It is in draft status with the IETF (the IETF sets standards for the web). Firefox Hello requires that users surrender copyright to their “content”, and to agree to IP and privacy contracts (“terms of service”) that, among other things, gives Mozilla and Tokbox an open-ended, unrestricted legal blank check.

    No user should be subjected to questionable legal contracts simply to use an open source communications protocol. Firefox Hello is deceptive in that users who are not aware of the implications of Mozilla and TokBok’s terms of service, or of the difference between open source protocols and services with onerous legal terms may unwittingly surrender information and rights that they wouldn’t otherwise agree too. In short, Firefox Hello should be regarded as malware or a bug, and certainly not a feature.

  2. dandan said on December 13, 2014 at 3:23 pm

    just installed the new FF beta on my android 4.2.2 and on 4.4 but there is no “mirror tad” under tools.
    any advices?

  3. bfulwiler said on December 12, 2014 at 4:39 pm

    Really nice job on the article. I found it because I wanted to reorder the search engines. The info helped me get the old manager back, IMO a much better feature. There has been enough negative said about the new interface already, so I need not say any more.

  4. Zsolt said on December 5, 2014 at 8:39 pm

    This mixed content crap is annoying. I’ve wasted a bunch of time figuring out why stuff doesn’t load. It turns out it’s this “most websites still work” garbage feature.

  5. Name said on December 3, 2014 at 11:08 am

    There is no hello video chat anywhere and not in plugins..? So where it is..?

  6. scalywg said on December 2, 2014 at 10:47 pm

    ahh thankyou: “ and set it to false” saved my brain…

  7. Uhtred said on December 2, 2014 at 9:04 pm

    In UK and updated to FF 34.0, short while ago… smiley button discovered in hamburger/customise menu dropdown,

    no change to search option

  8. Victor said on December 2, 2014 at 8:00 pm

    Well I guess setting yahoo as default search engine with the install is just as bad as setting google as default, but really…? Yahoo?? That’s sooooo 2001 It’s easy to set back to your own prefered SE, but what really makes me looking at Chrome more and more is that with every update several addons just stop working. With the last update 75% of the addons I’ve installed are switched off. Yeah I know the developers are probably working on it, but it happens with every update and is very annoying!! I’ve been promoting FF for years, but I guess the final change to another browser is very near……

  9. Mojose said on December 2, 2014 at 7:14 pm

    I signed up, i.e. first time commenter, just to give a big THANK YOU for the trick on how to disable that obnoxious, distracting catastrophe with the new Search Interface.

    Interestingly I also left a number of requests on how to disable that feature at various Firefox pages (respectfully and politely) and, yeah, guess what, they did not even publish/post the comments. smh. For years I was an unabashed fan and would recommend Firefox to anyone and everyone, but it seems at each update they do yet something else that is causing me to seriously look elsewhere.

    I also did not realize they are now in bed with Yahoo (which explains a lot), who also has perhaps the most horrendous reputation of excising constructive criticism, publishing mainly suspicious glowing reviews on their sites, all the while continuing to wedge their non-choices onto once-loyal customers.

    OK, OK, rant over, haha. But again, THANK you so much for this workaround and very informative article, I commend your efforts and expertise. After the FF update I had been searching everywhere to no avail, and you nailed it. Ghacks is now at the top of my bookmarked list.

  10. Ananda said on December 2, 2014 at 4:20 pm

    I was convinced I installed FF 34.0.5, but now, in the program itself, it says it is 34.0
    And I am also told it is up-to-date.

    Let’s not worry too much about the efficiency of the 21st century… It’s frustrating and does not help a bit.
    But you do not have to agree with it! :-)

  11. chesscanoe said on December 2, 2014 at 3:07 pm

    I got Fx 34.0 in US about 18:00EST 2014-12-01 and have observed no problems for what I actually do with the browser. On restart after install, if you look carefully at the Fx tab, there are options such as Search and Auto-Install to make, which I did, choosing Google and Notify Only on update availability. I’m glad the security fixes were implemented per:

  12. Roman Podolyan said on December 2, 2014 at 1:37 pm

    Thanks, Martin!
    The new v 34 search is so annoying for me, and you are the one who rescued me again! :)

  13. ilev said on December 2, 2014 at 11:11 am

    Yahoo = Bing

    Mozilla Firefox, Portable Edition 34.0.5 :

  14. Faiz said on December 2, 2014 at 8:55 am

    I correct myself. The FF 34 is not in the repo yet. actually it is out for Linux stable as I saw from the FF site

  15. Faiz said on December 2, 2014 at 8:49 am

    not out for stable linux version. eagerly looking forward to the browser based calling function. also, thank you mozilla for helping the tor project with your high-speed relays. yes, lets speed up free and open internet surfing experience.

  16. Dwight Stegall said on December 2, 2014 at 6:22 am

    Mine didn’t change to Yahoo as the default search. I removed Yahoo a long time ago. It can’t switch to what isn’t there. :)

    1. Faiz said on December 2, 2014 at 8:50 am

      open yahoo search page, click on the search bar on FF (beside address bar) and add yahoo search. The feature you are talking about, the default yahoo, is not out yet I guess. Moreover, you can always restore the default list of search engines to restore Yahoo.

  17. Kulm said on December 2, 2014 at 2:48 am

    I’m in the US. FF just auto updated to version 34.0.

  18. Pete said on December 2, 2014 at 2:13 am

    Almost 1 million users of Flashblock are for a surprise, the addon doesn’t work in Firefox 34! And there’s no real alternative.

    1. infogain said on December 2, 2014 at 8:59 am

      same here @Pate, so sad, is there an good alternative to FlashBlock or we sud wait for an update

    2. Faiz said on December 2, 2014 at 8:52 am

      guess the developers are working on it and will make it compatible soon. I personally dont use it, ghostery + ABD plus enough for me

  19. Randy Weinberger said on December 2, 2014 at 12:22 am

    Some people feel that Hello should be built as an add-on and should be able to connect to the PSTN. We happen to feel the same way, so we built FireRTC. We are looking for beta users, if you are interested in checking it out go to

  20. jimbo said on December 1, 2014 at 11:12 pm

    I’d 50 engines in a readable list … now tiny boxes with tinier icons … and 2 most used icons have GONE.
    Here we go again … appearance over functionality. Still, the idea was good if not the execution.

    1. Ray said on December 2, 2014 at 9:54 pm

      I don’t use the search bar anyway since it clutters up the UI so this doesn’t affect me :)

      I only use search keywords.

    2. Tom Hawack said on December 1, 2014 at 11:32 pm

      As stated by Martin in this article, setting to false restores the Search Bar to previous display/behavior, including sorting and keywords.

      I hadn’t tried it until right now because I imagined it wouldn’t restore the keywords/sorting features when in fact it does… needs a Firefox restart though.

    3. jimbo said on December 1, 2014 at 11:29 pm

      and the config switch doesn’t work
      and the improved offering cannot be re-arranged ?
      I do despair.

      1. Martin Brinkmann said on December 1, 2014 at 11:36 pm

        You need to restart your browser before the change takes effect.

  21. Tom Hawack said on December 1, 2014 at 10:43 pm

    I won’t use the Hello feature since it requires WebRTC which I’ve disabled. Still I do hope that those concerned by the Hello missing button will get the problem resolved.

    This update seems ok. The new Search Bar concept, not bad in itself, seems to no longer handle keywords. I see nowhere this feature. Also, a search engine can be disabled but not removed from Firefox. Only way I found was to close Firefox, remove an engine from the user’s profile / searchplugins folder, delete search.json and search-metadata.json and restart Firefox. This would normally clean up the metadata including keyword associated to a search engine, as well as the engines’ sorting. Since keywords seem unavailable as well as sorting what metadata handles I ignore, Deleting both json files above mentioned has them rebuilt on Firefox start in alphabetical order. Here I’ve set a 1-Engine name for Web Search engines, a 2-Engine name for Video Search etc in order to have the engines sorted by group. Complicated compared to before, and NO keywords, which I miss (typing GM Honolulu from the urlbar to have Google Maps search for Honolulu was great.

    This update seems unfinished.

  22. ACow said on December 1, 2014 at 9:47 pm

    > Firefox is already running on Windows fix

    Wow, some fix that is. Letting me forcefully kill a process, because profiles seem to get bungled after a while and won’t terminate/unlock properly. What a mess.

    I tried to fix the problem myself a few days ago. Disabling addons, starting in safe mode, resetting the profile did not help in any way. I had an earlier unbugged version of the profile backed up, so I just rolled back, but for an average user fixing the Firefox is already running bug means setting up a new profile.

  23. Francesc said on December 1, 2014 at 9:44 pm

    And now it is possible to synchronize passwords with the master password set.

    1. Martin Brinkmann said on December 1, 2014 at 9:47 pm

      Now that is good news.

  24. anohana said on December 1, 2014 at 9:33 pm

    Looks like I’m not the only one who has problem with Hello button. I hope an update will come soon.

  25. anohana said on December 1, 2014 at 8:41 pm

    I can’t find Hello.

    1. Martin Brinkmann said on December 1, 2014 at 8:50 pm

      There is a bug, maybe it applies to your issue?

      1. Gary said on December 1, 2014 at 9:42 pm

        That seems to explain it. But I still need to find out more about the loop throttled function.

        Okay, here is a link that seems to shed some light on the subject:

      2. Gary said on December 1, 2014 at 9:23 pm

        This is weird. A couple of moments ago I was reading this conversation. Like anohana, I couldn’t find Hello. After reading Martin’s response, I checked my Firefox configuration and changed the loop throttled setting from true to false. After restarting Firefox, Hello was there. I thought I would come back here and report that finding. But when I did, I found a response from anohana to Martin indicating that he had done the same thing and with the same results.

        I went back and checked this a couple more times. Then, when I came back here, anohana’s response to Martin was no longer here.

        Like I said, the whole thing is weird and will have to explore exactly what the loop throttled setting is designed to do.

      3. Martin Brinkmann said on December 1, 2014 at 9:30 pm

        Maybe edited and then caught in moderation. Should be there now.

      4. Jake said on December 1, 2014 at 9:20 pm

        Cant find hello also. Not even available as a button. 34.0

      5. anohana said on December 1, 2014 at 9:09 pm

        Thanks for the link.
        When I set in about:config the “loop.throttled” to “false” and restart there is the Hello button in the Additional Tools and Features, but when I set back “true” and restart Hello disappears.
        Just found this:

  26. Armond said on December 1, 2014 at 8:02 pm

    Just another great and informative article. Thanks!
    Interestingly, I see 34.0 release on the Mozilla’s FTP server, but there is another 34.0.5 release there?
    I downloaded the En-US version of the 34.0.5 for Windows and its default search engine is Yahoo?
    Good game Mozilla!:)

    1. Martin Brinkmann said on December 1, 2014 at 8:09 pm

      See my reply to Francis for information.

      1. Jeffrey Sheinberg said on December 10, 2014 at 12:26 am

        No, I did not restart my browser, since the search button on the options configuration was removed without

        Following your suggestion, I then tried restarting the browser, and now I can access the “Manage Search Engines” directly from the search bar.

        Thanks for the suggestion.

      2. Jeffrey Sheinberg said on December 9, 2014 at 9:37 pm

        I have FF 34.0.5 on Windows 8. Disabling the new search in about:config does _not_ re-instate any configuration
        for editing search engine keywords – however, my previously configured keywords still work.

      3. Martin Brinkmann said on December 9, 2014 at 9:42 pm

        Did you restart the browser?

      4. Gary said on December 1, 2014 at 10:19 pm

        That’s correct (and a good point to boot).

        From what I can see you can’t do that now in the new Options | Search box. If you follow Martin’s instructions above to change from true to false, then you’ll have the old search box back and can select Manage Search Engines to add and/or edit your keywords. However, you’ll lose the new Options | Search box in the process.

        Frustrating! And half-baked as well (although, for other reasons, Mozilla may want to get rid of keywords entirely).

      5. Jake said on December 1, 2014 at 9:50 pm

        Sooooo… How do I assign keys to search engines now??

      6. Martin Brinkmann said on December 1, 2014 at 10:13 pm

        It is not implemented yet. Only option is to disable the new search interface for now.

  27. Francis said on December 1, 2014 at 7:50 pm

    What the difference between 34.0 and 34.0.5?

    1. Martin Brinkmann said on December 1, 2014 at 8:02 pm

      Firefox 34.0.5 seems to contain Yahoo as the default search engine for Firefox US.

      From what I can gather, it seems that US users may get 34.0.5 while the rest will get 34.0. Confusing? Yep.

      Also, Yahoo will be the new default search engine for all US users who have not modified the search engine.

      1. Lookmann said on December 2, 2014 at 6:26 am

        HI Martin,

        On 28th Nov’ 2014, I installed FF 34 RC 2, which appeared as a full version in the ‘about FireFox’ window.
        It disabled my AiOS side bar, though.
        After so much trouble, I restored it from ‘customise’ options.
        I wish FF stops disturbing its long- time, loyal customers.

      2. Johnny said on December 2, 2014 at 3:30 am

        Yes i find it rather rude personally forcing yahoo to default just to register hits by pinging yahoo servers.
        I guess they need to show Yahoo a quick return on there investment by saying hay look at all the traffic now.

        What about the people who prefer Google as there default they should have made it optional not forced it i
        for one am not happy about this behavior by mozilla. forcing new tab ads on us now this i fear the path they are taking.

      3. Gary said on December 1, 2014 at 9:39 pm

        I have Firefox 34.0.5 installed. Like Martin says, it does make Yahoo the default search engine. But it goes far beyond that and in ways that I find pretty annoying to say the least.

        Prior to upgrading to Firefox 34.0.5, I had changed my default Firefox configuration in a number of ways related to the search function. For example, the Firefox configuration includes three keys labeled,, and By default, I believe was formerly Google (Yahoo was 2, I believe, and I cannot recall what was 3). I had changed these so my three defaults were Startpage Europe, Ixquick Europe, and DuckDuckGo.

        After the upgrade to Firefox 34.0.5 my defaults were still there. However, Firefox basically chose to override them by substituting three new keys labeled,, and For these new keys, which actually control the search function, Firefox inserted Yahoo as the default It also changed the defaults for & 3, inserting its own preferred search engines for mine.

        Firefox 34.0.5 also makes a ton of other changes to the default search keys, all of which seem designed to implement Mozilla’s new deal with Yahoo.

        While I appreciate Mozilla’s desire to enhance its revenue stream, I find it EXTREMELY ANNOYING that Mozilla feels like it can render my own search preferences invalid.

        This is really one of the worst things Mozilla has done and it certainly diminishes my confidence in the organization. But the point is that you need to check ALL of the search settings if you’ve customized the search function in the past because Mozilla apparently doesn’t care about preserving any choices you made.

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