Introducing Aurora 9

We have just released Aurora 9 (download and test Aurora 9), which is planned to be the upcoming Firefox 9. In it, we have a number of new things that we hope will get you excited!

JavaScript Type Inference

We’ve improved JavaScript performance once again with type inference. We’ve made significant improvements on both the V8 and Kraken benchmarks, and you should see real-world improvements to JavaScript performance as well.

JavaScript Interface for Do Not Track

Firefox 4 introduced Do Not Track, and now there is a way to detect a users’prefence through JavaScript as well:

mouseenter and mouseleave events

For some time now, web developers have been struggling with handling mouseover and mouseout events on elements, since when child elements have gained focus, the event has bubbled up and triggered mouseout on the parent element – something you would in most cases not like to happen.

Therefore, we are now happy to introduce support for mouseenter and mouseleave events:

Camera UI for Mobile

You can now use an input element to trigger a native app to take pictures. Please try the Camera UI for Mobile demo.

Support for chunked XMLHttpRequest

When doing XMLHttpRequest requests with large data sets, you can now get partial data as it arrives instead of waiting for it all to show up. You can use this to build more responsive and more efficient web sites.

Other changes

We’ve also got support for a bunch of other changes as well. These will be added to the Firefox 9 for Developers page over the next few weeks.






About Robert Nyman [Editor emeritus]

Technical Evangelist & Editor of Mozilla Hacks. Gives talks & blogs about HTML5, JavaScript & the Open Web. Robert is a strong believer in HTML5 and the Open Web and has been working since 1999 with Front End development for the web - in Sweden and in New York City. He regularly also blogs at and loves to travel and meet people.

More articles by Robert Nyman [Editor emeritus]…


  1. Jason

    So 3D transforms just missed the code merge to Aurora?

    Other than that, font-stretch is long overdue, I don’t think any other browser out there actually supports that property.

    September 30th, 2011 at 16:55

    1. Mark

      Yep, seems it landed in the Nightlys today:

      September 30th, 2011 at 18:32

  2. Liz

    OK, I quit using Aurora yesterday after the 12th Google crash, probably 20th overall. Did this release fix that? I’ve been using 7.01 Firefox since. No crashes, no nothing. Aurora had been working PERFECTLY prior to the update a few days ago.

    September 30th, 2011 at 18:55

    1. meh

      Well, that’s what you should expect. Aurora gets more stable with time, but after each merge (accompanied by a version bump) it gets unstable again. Consider using betas if this is a problem.

      October 1st, 2011 at 05:56

    2. Boris

      Liz, did you file a bug? If not, could you please? Or at least list the information for those crashes from about:crashes here?

      October 1st, 2011 at 15:10

      1. Liz

        I’m a clutz, I searched and this was the first place I could find to type stuff. Point me at the page. I didn’t put my name on the trouble windows and it was about the third time when I figured out what was consistent. Fire away, captain, so that I can do a proper bug report!

        October 1st, 2011 at 21:10

        1. Boris

          Your name doesn’t have to be on the crash reports; if you open “about:crashes” in Firefox it will give you links to those reports.

          As far as filing a bug, start with and just make sure to put the information from your about:crashes in the bug description. You’ll have to create an account, of course.

          Alternately, you can just mail the about:crashes information to me at

          October 1st, 2011 at 21:35

  3. Jonas Sicking

    It’s generally quite intentional that big features land right after a aurora branch and thus “just miss the merge”. We prefer to let big features like that bake in nightlies for 6 weeks as to ensure that we fix any bugs, rather than rush it in.

    It’s better for developers to not have to work around a buggy implementation than to have it 6 weeks earlier.

    September 30th, 2011 at 19:16

  4. Tim Niiler

    Will any work be done on SVG, specifically with the baseline-shift attribute of the tspan? This is useful for displaying exponents, and still doesn’t work properly in FF. *Is* work on SVG support still continuing, or is it basically being suspended since canvas is getting so good?

    October 1st, 2011 at 06:05

    1. Boris

      Tim, there’s lots of work happening on SVG, and especially on SVG text.

      October 1st, 2011 at 15:11

  5. RyanVM

    @Tim – There’s a lot of SVG work still going on, especially in the SMIL area. With respect to baseline-shift, it appears that bug 308338 is filed for adding that, but that development stalled out on it last year after spec questions came up. It may be worth pinging in that bug to see where things stand.

    October 1st, 2011 at 07:23

  6. Jesper Kristensen

    I tried the Camera UI demo, but it doesn’t seem to work :(

    October 1st, 2011 at 09:28

  7. greg russell

    Will it have the new types?

    October 1st, 2011 at 12:37

    1. greg russell

      *New Input types (didn’t like the < I put in there…)

      October 1st, 2011 at 12:38

      1. Robert Nyman

        It does not have user interfaces implemented to the same extent as some some competing web browsers, no. There is a lot of discussion how these should be implemented, and we want to get it as right as possible the first time around.

        With that said, we are very well aware of the need to take this further, and personally I hope it will be in the near future.

        (For those interested in HTML5 Forms, I wrote a long blog post on what it offers: HTML5 Forms input types, attributes and new elements – demos, tips and tricks)

        October 1st, 2011 at 19:18

  8. besr

    Is very good Fx9, but i dont know why is named 9.0a2 if is only the first release of the aurora channel

    October 1st, 2011 at 14:54

    1. Sean McArthur

      It is a2 because a1 is the Nightlies. Once it gets to Aurora, its a2. Once it’s in beta, it’s b#. :)

      October 12th, 2011 at 10:10

  9. Benoit Jacob

    Tim, work is definitely going on SVG, as there are at least 2 or 3 developers on it… search the hg logs or bugzilla for svg to get details.

    October 1st, 2011 at 15:09

  10. Aryeh Gregor

    The DOM4 spec was updated three weeks ago to say that node.contains(node) should be true, to match browsers:

    October 2nd, 2011 at 11:16

    1. Robert Nyman

      Great, thanks!

      October 2nd, 2011 at 16:48

  11. j.j.

    > We now support document.caretPositionFromPoint.

    No longer (backout of bug 654352)

    October 8th, 2011 at 11:53

  12. marc

    document.body.onundo and onredo should be implemented per HTML5 spec, either on document body only or on any specified element, preferably the latter

    October 19th, 2011 at 01:07

    1. Robert Nyman

      I hope it will be supported in a good fashion, but I don’t have a timeline for that.

      October 19th, 2011 at 02:24

  13. Saeed Neamati

    Guys, guys. Slow down. I still haven’t get used to Firefox 7. I think you have mistaken the minor version with the major version (just like Chrome).

    November 1st, 2011 at 05:48

    1. Robert Nyman

      Version numbers are a bit relative, but rapid releases makes it possible for us to improve the web browser on a more regular interval than once a year or similar, which we hope both end users and web developers will gain from.

      November 2nd, 2011 at 08:38

  14. Brad

    Will FF9 support caching flash files? If you go to youtube at the moment, watch a video, then watch it again, the second play through redownloads the entire video. This is very problematic as bandwidth restrictions are becoming more prevalent, and this seems like a huge waste of bandwidth.

    November 4th, 2011 at 01:38

    1. Robert Nyman

      To my knowledge, not now, especially when it comes to streaming data. I do understand the problem, though.

      November 4th, 2011 at 08:48

  15. friesecustoms

    I’m Kinda new to firefox, so help me out a bit. Aurora is like a Beta version of Firefox, or am I way off here. Sorry, just trying to learn and understand

    April 5th, 2012 at 21:45

    1. Janet Swisher

      Aurora is earlier than Beta (which Firefox also has), but more stable than Alpha (which Firefox does not have) or Nightly. Features in Aurora are most likely going to go into a release, but are still experimental. See the Aurora download page.

      April 6th, 2012 at 09:27

  16. Logan

    does it work with android 2.3.3

    June 22nd, 2012 at 16:48

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