Firefox 3.6 was released on Jan 21st and has already been downloaded more than 35 million times! It features a faster JavaScript engine, faster DOM performance and a bunch of new HTML5 features. Highlights for web developers include support for the WOFF font format, new CSS features like gradients and multiple backgrounds, drag and drop, File API, device orientation, and more. Want to see the full list? Look at our Firefox 3.6 for Developers page on developer.mozilla.org.

We hope that you took the time to test Firefox 3.6 on your web sites before the release. If you didn’t, it’s not too late to let us know about issues. Here are a few problems that we’ve seen in the wild so far:

  • We’ve seen a couple of issues with the FCKEditor component, used widely on the web. It apparently doesn’t handle dates after 2009 properly (this is the first major browser release in 2010, a new decade!) and it also has some problems with document.readyState.
  • People who had the YSlow extension installed saw crashes with Firefox 3.6. YSlow has been updated to version 2.0.6 to fix the issue
  • Some Facebook apps were broken by a change we made to comply with the upcoming HTML5 standard. We updated element.getElementsByTagNameNS and document.getElementsByTagNameNS to no longer case-fold when doing tag name lookups. (We strongly suggest that you only use lower-case for tag names for many reasons, including this.) For more information, please see this note from Henri Sivonen about what’s changed. Facebook has since fixed the issue in their code, but other sites may also be tripping over this.

We’re looking for feedback on any developer-facing regressions you’ve seen in 3.6 from 3.5. Please comment on this post if you have feedback.

76 comments

Post a comment

  1. Ad Bouwen wrote on May 19th, 2010 at 12:45 am:

    I updated FF from 3.5.9 to 3.6.3, but al the time FF spontaneously goes back to 3.5.9. Anybody the same experience? And what is the solution?
    Ad (The Netherlands)

    Reply

  2. Lauren wrote on May 25th, 2010 at 7:53 am:

    @Ad Bouwen: I have the exact same issue in my work enviro, but instead of 3.6.3, I have 3.5.5 and it CONSTANTLY downgrades to 3.0.6. If I close out all instances of the browser and re-open it, it will upgrade to 3.5.5. Very bizarre…

    Reply

  3. Donnie Reese wrote on June 21st, 2010 at 3:40 pm:

    I am having trouble getting web fonts to show up on all computers. I check that the correct version is being used, and they are all windows-based installs, but some computers refuse to show web fonts. I can’t seem to find any instance of why this may be happening.

    Reply

  4. Ad Bouwen wrote on June 23rd, 2010 at 11:20 am:

    After I removed older versions of Firefox my “downgradeproblem” is over.

    Reply

  5. mozillagorilla wrote on June 24th, 2010 at 10:38 pm:

    Mozilla Firefox version 3.6 was a forced update on my computer by Mozilla. I would have never allowed it because now my realplayer downloader doesnt even work at all, and when I researched the problem, found out realplayer doesnt support F.F. v3.6 BOGUS! Is there anyway to disable the upgrading of mozilla firefox from the version prior to this one if I uninstall, and reinstall? Why dont you program twits leave well enough alone

    Reply

  6. Ms.Snow wrote on August 5th, 2010 at 8:09 pm:

    I would really like to see firefox give us a little more room in the plugin section. I really resent not being able to permanently remove a plugin. The enable/disable feature is stupid… If I dont want a plug in in there at all I have to put up with it being there in disabled mode. Plus the automatic detection of a bunch of plugin’s that I never wanted in the first place take over that section and I cant get rid of them. Please Please Please give us a feature that lets us remove what we dont want there.
    I also would like to customize how my tool bar fits together the size and places that each feature is shown.

    Reply

    1. Dieng Nguyen wrote on March 12th, 2011 at 7:18 am:

      I like your comment very much, Ms Show. Your comment is what I really want to let Firefox know.
      Always give us choices, please.
      I have three browsers on my computers: IE, Firefox, and Chrome. However, I only use firefox because I have the freedom to choose. So don’t take away my freedom. It is the most important feature that keep me stay with Firefox.

      Reply

  7. Mark wrote on October 6th, 2010 at 9:38 am:

    URL Manager Pro 3.5 b11 works for me in with Firefox 3.5.8 but not in Firefox 3.6

    So what gives here? They fixed it for 3.5.8 and broke it again in 3.6?

    Makes no sense to me.

    Reply

  8. Mary Vogt wrote on October 7th, 2010 at 1:39 pm:

    I am having horrible problems with FireFox 3.6.10. Especially typing lag, and freezing, and videos playing choppy. My computer is only 8 months old, I have super-high performance DSL and plenty of memory, etc.

    I can concur what Rex said. The longer it’s open, the worse it gets. I can’t even get the menus to drop down faster than like 15-20 seconds! It’s unbelievable.

    Has anyone found a solution? If not, I’m switching to Opera or Safari.

    I am running Windows 7 OS.

    Reply

  9. milt brewster wrote on October 13th, 2010 at 11:33 am:

    Too many connectivity and usability problems with FF3.6.9 and FF3.6.10 to list here.

    The latest: FF simply refused to connect via port 80, even while Thunderbird and Chrome connected. Upon clicking on a bookmark, the url appeared in the tab (not the title), and either a “remote site reset” FF error page appeared, or FF just hung. Safe mode was OK but very slow.

    I uninstalled; downloaded and reinstalled FF3.6.10, and it still wouldn’t connect. I then downloaded FF3.5.13, installed it — and it runs fine.

    I want HTML5 and the new JavaScript engine, but application basics have to be bulletproof: Connectivity; basic functionality; add-on operation; basic malware protection. In my user’s opinion, FF3.6.9 and FF3.6.10 were not ready for release. I know that you guys know these things already, and I look forward to a really robust release in the near future.

    milt brewster

    Reply

  10. dissapointed wrote on October 16th, 2010 at 10:59 pm:

    i have been updating my firefox recently to firefox 3.6
    and shockingly, i cannot browse facebook nor tumblr after upgrading the firefox 3.6
    whats the problem actually?
    i hope the corporation can repair or reboot their system and please dont ask the consumer to update if you guys are not ready for upgrading your own performances. i am so dissapointed. ._.

    Reply

  11. Rashmi wrote on October 22nd, 2010 at 9:25 am:

    Firefox 3.6.11 is freezing with yahoo mail application. it is getting stuck with loading yui api’s or a geo package. Performance of this browser seems to be lower than the 3.6.3 on xp sp2 machine.

    Reply

  12. J Davis wrote on November 16th, 2010 at 7:22 pm:

    Started building an upgrade to my website. It runs well on Safari, Chrome, IExplorer, FIreFox 3.5 but not when tested with Firefox 3.6 …my problem concerns where div and iframes are placed by the browser (v3.6) using CSS rules. Apparently, something very important broke in the new release.

    Is unpredictable result via CSS rules a wide spread problem using the latest release?

    Cheers, Jim

    P.S. The upgrade to my site has not been uploaded to the server. I would it to run version 3.6 first.

    Reply

  13. Paul wrote on December 13th, 2010 at 5:54 pm:

    I had to download the version for yahoo.ca & everything works proper & great till it up dates to the 3.6 thing then the yahoo email treats every email out going like spam so I turned the auto updates to ask & then ignore it or if I update it fails the emails again & again.So maybe you should try to figure out what you did wrong & go back to what works,Don’t believe me .go to yahoo answers & just read the hundreds of angry & upset folks concerns there.
    as a mechanic the experiance teaches “IF IT AIN’T BROKE, DON’T FIX IT”

    Reply

  14. Colin Porter wrote on January 31st, 2011 at 9:07 am:

    I am not a developer but have used FF since 2003. Since the update that changed the way that FF handles Adobe Flash crashes life has been difficult for anyone wanting to watch flash videos via FF. Previously Flash crashes happened maybe once a month, causing the browser to crash as well. Now I can experience 10 or more failures of Flash EVERY day. mI have read as many articles as possible and implimented all suggestions all to no avail. I have also tried FF 4 beta to no avail. Either get this sorted or lose a great many FF users to other platforms. I am now seriously looking at Opera and even IE because this issue is driving me round the twist – GET IT SORTED.

    Reply

  15. Preston Brown wrote on January 31st, 2011 at 12:19 pm:

    As other users have found, watching video via firefox ultimately makes it crash. I’ve looked at the Task Manager while Firefox is running and it just consumes more and more operating memory. It does not purge as you watch, just keeps eating more. The last time it crashed it became impossible to reboot and worse yet I cannot even uninstall it !!! I am at a loss, I want if off my machine for now and cannot accomplish this. Anyone with a solution? It would be greatly appreciated.

    Reply

  16. paul wrote on January 31st, 2011 at 10:14 pm:

    I guess i was lucky as mine did work but you guys got to say perfect the number instead of uping the number with some new tricks but not fixing the last problems & stop with the “BETA” crap.
    Its the best browser but you guys are as sick & twisted as microsoft as you think the numbers must be upped as the microsoft folks do.Mostly they do that because explorer is so full of holes & with a built in hole from day one they make their numbers go up because they can’t fix the last one but sell the puke & white wash to the general public to make them think they have made improvments where its just the same old dog ! Mocrosoft is in the busness of selling software so expect they will continue to up the number while the fools rush out for the new..Its seems firefox is trying to do the same but not so scitzophrenicly in detail as microsoft.
    Kind oof like the north american auto market with its built in flaws!

    Reply

  17. Mireille Grovier wrote on March 4th, 2011 at 1:38 pm:

    Does anyone know how to export Bookmarks from Firefox 3.6.13 into Safari and/or Opera? Firefox is not letting me do this.

    Reply

  18. Susan Ganiebny wrote on November 4th, 2011 at 8:19 am:

    I`ve just gone back to 3.6 having used 7 for a short time and 7 drives you nuts! In 7, after about 10 mins, you constantly have to move the mouse around to get a page to load no matter what tips you follow from Mozilla, it`s absolutely crazy. I wouldn`t go back to using 7 if they paid me. I only upgraded because 3.5 kept crashing on Windows 7

    Reply

  19. Ponyboy2z wrote on December 10th, 2011 at 9:02 am:

    I am having trouble reaching specific websites to pay bills. When I type in the address and press go Firefox 3.6 redirects me to all different sites. I cannot reach the address that I type in. I keep getting redirected to sites I do not want. This makes Firefox 3.6 worse than useless because I cannot do the simple basic step of entering a known address and going there.

    Reply

    1. Janet Swisher wrote on December 12th, 2011 at 3:23 pm:

      It sounds like your computer is infected with malware. See this support article for help. In general, the Firefox Support site is a better place to get support than commenting on a blog.

      Reply

1 2

Add your comment

  5.