Firefox 15, What's New

Martin Brinkmann
Jun 5, 2012

Mozilla is preparing to update all different Firefox channels in the coming days. We have already mentioned that the stable channel update is already available, while users of the beta and aurora channels still have to wait for the updates to be released to their channels. As always, I'm looking at the changes in the Aurora channel, and then at the same version again when it is released to the stable version. If you are a beta channel user, check out the Firefox 14 review instead dating back six weeks.

As always, there may be features planned for Firefox 15 that have not been integrated fully into Aurora, or have been integrated but disabled by default.

Some Windows users may experience faster startup times of the web browser thanks to improvements in this area. Mozilla basically wants to disable prefetch for Firefox on the system to speed up the browser's start. You can read up on some of the testing that was done and the discussion of the improvements. It needs to be noted that not every tested was noticing a startup speed improvement. Basically, Firefox users with lots of stuff going on should see performance improvements, while users on new or fast systems may not see much of a difference, if at all.

As far as performance improvements are concerned, Firefox 15 may also see an implementation of the incremental garbage collection feature that reduce the time individual garbage collections which in turn reduces the wait time for the user.

Another change that I have already talked about are the new in-content preferences, even though it is not clear yet if the feature will be enabled by default in Firefox 15 or a later version of the browser. I did notice issues with the feature during tests as extensions that added their own menu items to the dialog were not featured yet after enabling in-content preferences in the browser.

It also looks as if the final component of Firefox's Silent Upgrade feature will make its way into version 15 of the browser. We have talked about the feature previously, and I suggest you look at the article to find out what it is all about. In short, Mozilla attempts to reduce the time users have to wait until a browser update completes.  The last part of the feature are background updates, which basically means that the majority of the updates will be installed while Firefox is still running.

The new web apps feature had been implemented into Firefox 14 but was disabled there, and it appears that it will be enabled in Firefox 15. Mozilla describes web apps in the following way:

Web applications are universal applications. The run on any device. They use standard technology that works on desktop PCs, smartphones, and tablets. They can be installed on devices automatically when users authorize their devices, and are personalized so that users keep their preferences and data with them wherever they go.

Check out the overview here for additional details about the feature.

Firefox 15 may also be the first version of the browser that the new Social API gets tested in. Mozilla plans to deliver the feature as an add-on first before it will get integrated into the browser natively.  You can read more about the Social API and its integration into the browser here.

Web developers get a whole assortment of new tools and improvements. One of the new features is a command line for developers that developers need to activate currently before it becomes available. What they need to do is enter about:config into the address bar to set the devtools.toolbar.enabled preference to true. A restart of the browser enables the feature, which you can then activate with the shortcut Ctrl-Shift-V.

firefox command line web developer

While designed with web developers in mind, Firefox users can also use the new command line feature to change preferences in the browser without opening the about:config dialog at all. Entering help will get you started.

The bar lists buttons on the right that developers can click on for additional functionalities like opening the web console or activating the Inspector.

Check out Sören Netzschel's overview on the new features (via Bing Translate).

The update for Firefox Aurora to bring the version to 15 will be available shortly on this page and via the browser's internal updater.


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  1. Kunal Sharma said on September 2, 2012 at 7:25 am

    I am going to install new Firefox after reading that.. :)

  2. Raj said on August 29, 2012 at 2:01 pm

    Its official and Firefox 15 is now available for download..

  3. Ramon Zarat said on August 28, 2012 at 12:17 am

    Personally, what bug me the most is definitively the *constant* crash of the flash plug-in.

    I understand that it might not entirely be Firefox fault, but AFIK, other browser don’t suffer the same level of embarrassing instability. If I look at a video on youtube, then select another one, and then go back one page to the previous one, chance are very high the plug-in container will crash. My machine is otherwise 100% stable (prime95, Intel burn test, 3Dmark loop etc…), all drivers, firmwares and BIOS fully updated.

  4. RobertMNixon said on June 9, 2012 at 8:48 am

    Waiting for Nightly update 16.0a1. BUT it wont update 16.0a1 since stop update last on May 22nd!! I’m disappoint w/ Mozilla needs fixing my Nightly MUST update 16.0a1, damn it!


    1. Martin Brinkmann said on June 9, 2012 at 9:01 am

      Robert, that was a bug. You need to download it manually. See

  5. AC said on June 6, 2012 at 6:47 am

    The biggest improvement in Firefox 15 is bug 695480.

    This means that leaky add-ons are a thing of the past.

    Firefox itself performs just fine but the add-ons have been a problem for a long time. This wonder patch will put an end to the add-ons being the source of all the problems, which in turn means that Firefox will no longer be incorrectly blamed for the performance problems of the add-ons that people have running with it. So after August 28th, if someone is bitching about Firefox being slow, it’s either their hardware, OS or other software, or they’re running version 14 or earlier.

    This is the single biggest bug fix that has landed in a LONG time and yet it’s not something they’re shouting about. It will solve a lot of problems for millions of people and could be a game changer at least in the short term.

  6. Karl Gephart said on June 6, 2012 at 1:24 am

    Hate to disappoint. I tried Waterfox on Win7 64bit and it just slowed down my entire OS. Was fast at first. That didn’t last. I agree with you, Mozilla needs to SERIOUSLY address the memory leaks. Firefox 15 development tools do look hot, though…there will be a nice fluidity tool for all screen sizes (i.e., mobile testing)..

    1. boris said on June 6, 2012 at 1:38 am

      I understand that developers need some love, but web browser is a consumer market. If consumers leave because of bad performance, Firefox is toast.

      1. Midnight said on June 6, 2012 at 6:18 pm

        hundreds of million. :)

      2. Midnight said on June 6, 2012 at 6:18 pm

        Firefox will never be toast, not with the hundreds of mioon users who use and support it. :)

  7. boris said on June 5, 2012 at 9:51 pm

    I just wish they would fix memory leaks first before going to million endeavours and bloating Firefox even more. I get 2GB of Firefox memory after 8-10 hours. At least make it 64bit. This way memory leaks will not affect responsiveness so much.

    I am tired of it. Trying Waterfox now.

    1. Ryan said on June 25, 2012 at 1:52 am

      Don’t bother with Waterfox, get Pale Moon instead. There’s a 64bit version that I’m running.

      1. Ramon Zarat said on August 28, 2012 at 12:09 am

        Please, be more specific and provide some arguments as to *why*, in your opinion, Pale moon is a better choice. I’m asking because every single Pale moon VS Waterfox benchmark I’ve looked at give Waterfox as the faster solution. Maybe I’m missing something here.

    2. sut said on June 6, 2012 at 1:25 am

      Before ditching Firefox I urge you to try Firemin. Wave goodbye to Firefox memory leaks..

      1. Ramon Zarat said on August 28, 2012 at 12:00 am

        This is simply a memory manager, as tons of other already exist. I rather use a more specific and appropriate tool to manage my memory and the one I use is called memory cleaner. It’s available here:

      2. Midnight said on June 6, 2012 at 6:16 pm

        Thanks for the tip. I’ll check this out. :)

  8. Ahmad said on June 5, 2012 at 7:11 pm

    Firefox 15 also got:
    1) More contenteditable support
    2) New JS Based DOM Bindings for several stuff
    3) Addon leak major cause fix
    4) Compartment per Global
    5) HTML5 Data View support

    and much much more.. It is one hell of browser and its development was epic..

  9. Midnight said on June 5, 2012 at 6:04 pm

    Thanks for keeping us up to date on the Firefox improvements, Martin.
    Very helpful.

    I just updated Firefox UX (Nightly) 15.0a1 and got 16.0a1, which works fine!
    Nice to know that the developers at Mozilla are working hard at making their Browser faster and more secure! :)

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