Firefox 5 is here

Today, three months after the release of Firefox 4, we release Firefox 5, thanks to our new development cycle. Developers will be able to create richer animations using CSS3 Animations. This release comes with various improvements, performance optimization and bug fixes.

CSS3 Animations

CSS Animations (check out the documentation) are a new way to create animations using CSS. Like CSS Transitions, they are efficient and run smoothly (see David Baron’s article), and the developers have a better controls over the intermediate steps (keyframes), and can now create much more complex animations.

Notable changes

Other Bug Fixes and Performance Improvements:


  • All HTML elements now have the <a class="new" href="">accessKey</a> attribute, as well as the <a href="">blur()</a> , <a href="">click()</a> , and <a href="">focus()</a> methods. These are specified in the <a href="">HTMLElement</a> interface.
  • In order to comply with the HTML5 specification, support for the UTF-7 and UTF-32 character sets has been removed.
  • When in quirks mode, empty <a href=""><map></a>s are no longer skipped over in favor of non-empty ones when matching. See the Gecko notes on the <a href=""><map></a> element for details.
  • Firefox mobile on Android now supports WOFF fonts for <a href="">@font-face</a> .
  • WebGL no longer loads textures from domains other than the originating domain, as a security measure.

Canvas improvements

  • The <a href=""><canvas></a> 2D drawing context now supports specifying an ImageData object as the input to the createImageData() method; this creates a new ImageData object initialized with the same dimensions as the specified object, but still with all pixels preset to transparent black.
  • Specifying non-finite values when adding color stops through a call to the <a href="">CanvasGradient</a> method addColorStop() now correctly throws INDEX_SIZE_ERR instead of SYNTAX_ERR.
  • The <a href="">HTMLCanvasElement</a> method toDataURL() now correctly lower-cases the specified MIME type before matching.
  • getImageData() now correctly accepts rectangles that extend beyond the bounds of the canvas; pixels outside the canvas are returned as transparent black.
  • drawImage() and createImageData() now handle negative arguments in accordance with the specification, by flipping the rectangle around the appropriate axis.
  • Specifying non-finite values when calling createImageData() now properly throws a NOT_SUPPORTED_ERR exception.
  • createImageData() and getImageData() now correctly return at least one pixel’s worth of image data if a rectangle smaller than one pixel is specified.
  • Specifying a negative radius when calling createRadialGradient() now correctly throws INDEX_SIZE_ERR.
  • Specifying a null or undefined image when calling createPattern() or drawImage() now correctly throws a TYPE_MISMATCH_ERR exception.
  • Specifying invalid values for globalAlpha no longer throws a SYNTAX_ERR exception; these are now correctly silently ignored.
  • Specifying invalid values when calling translate(), transform(), rect(), clearRect(), fillRect(), strokeRect(), lineTo(), moveTo(), quadraticCurveTo(), or arc() no longer throws an exception; these calls are now correctly silently ignored.
  • Setting the value of shadowOffsetX, shadowOffsetY, or shadowBlur to an invalid value is now silently ignored.
  • Setting the value of rotate or scale to an invalid value is now silently ignored.


  • Support for CSS animations has been added, using the -moz- prefix for now.


  • The <a href="">selection</a> object’s modify() method has been changed so that the “word” selection granularity no longer includes trailing spaces; this makes it more consistent across platforms and matches the behavior of WebKit’s implementation.
  • The <a href="">window.setTimeout()</a> method now clamps to send no more than one timeout per second in inactive tabs. In addition, it now clamps nested timeouts to the smallest value allowed by the HTML5 specification: 4 ms (instead of the 10 ms it used to clamp to).
  • Similarly, the <a href="">window.setInterval()</a> method now clamps to no more than one interval per second in inactive tabs.
  • XMLHttpRequest now supports the loadend event for progress listeners. This is sent after any transfer is finished (that is, after the abort, error, or load event). You can use this to handle any tasks that need to be performed regardless of success or failure of a transfer.
  • The <a href="">Blob</a> and, by extension, the <a href="">File</a> objects’ slice() method has been removed and replaced with a new, proposed syntax that makes it more consistent with Array.slice() and String.slice() methods in JavaScript. This method is named mozSlice() for now.
  • The value of <a href="">window.navigator.language</a> is now determined by looking at the value of the Accept-Language HTTP header.


  • Regular expressions are no longer callable as if they were functions; this change has been made in concert with the WebKit team to ensure compatibility (see WebKit bug 28285).
  • The Function.prototype.isGenerator() method is now supported; this lets you determine if a function is a generator.


  • The <a href="">class</a> SVG attribute can now be animated.
  • The following SVG-related DOM interfaces representing lists of objects are now indexable and can be accessed like arrays; in addition, they have a length property indicating the number of items in the lists: <a class="new" href="">SVGLengthList</a> , <a class="new" href="">SVGNumberList</a> , <a class="new" href="">SVGPathSegList</a> , and <a class="new" href="">SVGPointList</a>.


  • Firefox no longer sends the “Keep-Alive” HTTP header; we weren’t formatting it correctly, and it was redundant since we were also sending the <a href="">Connection:</a> or <a href="">Proxy-Connection:</a> header with the value “keep-alive” anyway.
  • The HTTP transaction model has been updated to be more intelligent about reusing connections in the persistent connection pool; instead of treating the pool as a FIFO queue, Necko now attempts to sort the pool with connections with the largest congestion window (CWND) first. This can reduce the round-trip time (RTT) of HTTP transactions by avoiding the need to grow connections’ windows in many cases.
  • Firefox now handles the Content-Disposition HTTP response header more effectively if both the filename and filename* parameters are provided; it looks through all provided names, using the filename* parameter if one is available, even if a filename parameter is included first. Previously, the first matching parameter would be used, thereby preventing a more appropriate name from being used. See bug 588781 .


Developer tools

  • The Web Console’s Console object now has a debug() method, which is an alias for its log() method; this improves compatibility with certain existing sites.

About louisremi

Developer Relations Team, long time jQuery contributor and Open Web enthusiast. @louis_remi

More articles by louisremi…


  1. Michael Butler

    Great work guys!

    June 21st, 2011 at 07:37

  2. Skatox

    Congratulations for your hard work! Now Firefox it’s getting better than ever!!

    June 21st, 2011 at 07:40

  3. Brandon

    I Thought is was already out, because i have had it for at least a month now

    June 21st, 2011 at 07:51

    1. Jwalant Natvarlal Soneji

      Yeah, and that could be your FF 5 alpha/beta.
      Firefox Release Roadmap:

      June 22nd, 2011 at 12:55

  4. 3615Buck

    Almost as good as Chromium…

    June 21st, 2011 at 07:57

  5. Broken Skeleton

    I can’t figure out why this is FF 5 and not 4.1?

    June 21st, 2011 at 08:11

    1. louisremi

      Because we switched our development cycle: now we release new major versions approx. every 6 weeks.

      June 21st, 2011 at 08:30

      1. Samuel

        Every 6 weeks? Why? That means be having nearly 9 “major” releases every year. So basically, by this time next year, we’ll be rocking Firefox 13, and preparing for version 14. Awesome. Frankly, this is a minor update and should be Firefox 4.0.2 or 4.1.0. Making it Firefox 5 makes absolutely no sense, as there were no major features added. Plus, half of my extensions were broken thanks to the version number being so drastically changed. Is this what we have to look forward to every 6 weeks? Hooray… Thanks, Mozilla.

        June 21st, 2011 at 11:13

        1. Ryan

          That’s been remedied, too:

          June 21st, 2011 at 12:39

        2. Broken Skeleton

          I’m glad someone else thinks the same way I do, I was starting to feel bad for not saying congratulations for a job that they should be doing. Don’t get me wrong I love firefox but these releases are a little silly.

          June 21st, 2011 at 23:21

          1. Ricardo

            Congrats on the great work, but I disagree on the version numbers. Having so many “major” versions will cause people to fell confuse… I was still convincing people to migrate from 3.* to 4…
            And it will be strange to have FF 14, 15… etc

            June 22nd, 2011 at 06:55

          2. Anna

            I agree.
            And now I have something that looks like a bug: no favicons on some tabs. And sometmes there is no link in address bar!
            Probebly, one of my addons causes this…
            This is very upsetting.
            Thougth, what is good: Firefox 5 is much more fast!

            June 22nd, 2011 at 09:38

        3. Stefan Mielke

          Yes, this is really not smart. We had a major release with Firefox 4 and now this, just a 4.1 saying “I’m rocking now!”. Sorry, but fixes and minor “improvements” are NOT a major release, and just going “Google way” is not necessarily a “good way”.

          June 22nd, 2011 at 10:39

  6. Gerald

    3 month between 4 and 5 ?? That was fast !


    June 21st, 2011 at 08:22

  7. Markus Klug

    Thanks for your hard work!
    But please fix the font rendering with the next release, so that I can finally turn on hardware acceleration (gfx.direct2d) again.

    Kind regards!

    June 21st, 2011 at 08:22

  8. Moe

    This is a new “version?”

    June 21st, 2011 at 08:24

  9. Ozzypig

    Awesome. Although I’m a diehard Chrome fan, I love to see other browsers stepping up the competition.

    Great work Mozilla :D

    June 21st, 2011 at 08:25

  10. Jon Reid

    Awesome new release schedule. Look forward to the fast bug fixes for sure. I know a few fellow devs were getting tired of the crashes. I held on a bit longer. Here’s hoping this release rocks :)

    June 21st, 2011 at 08:41

  11. pd

    Hooray, a new **MAJOR** version. Upgrade now for all the new goo…

    wait a minute, DOWNGRADE to version 5 and watch all your extension functionality DOWNGRADE as notoriously slow Add-On devs failed to kick their extensions despite there being *BUGGER ALL* changes for a ??? MAJOR ??? version?

    What a joke.

    June 21st, 2011 at 09:11

    1. Erunno

      Strange, all of my 21 extensions work, including 1-2 obscure ones.

      June 21st, 2011 at 12:17

  12. tong

    Great! Thank you very much!

    June 21st, 2011 at 09:16


    Great work .Thanks for your hard work!.

    June 21st, 2011 at 09:18

  14. Fatih

    Great work guys! That was really fast.

    June 21st, 2011 at 09:23

  15. Jamo

    More lovely CSS3 that we can play with mmmmm…..

    June 21st, 2011 at 09:26

  16. David

    New major version every 6 weeks, so we’ll have Firefox 10 around new years eve?

    June 21st, 2011 at 09:36

    1. laz


      June 22nd, 2011 at 06:36

  17. Mike

    Glad to see another update. I just hope the constant crashing is fixed!! Nothing more annoying then that!

    June 21st, 2011 at 09:44

  18. zenwalker

    Great work guys. U guys rock. Keep it up folks. Luv ya work!!

    June 21st, 2011 at 09:44

  19. Albert

    Great work. I like the CSS3 Animations feature. But expecting “Firebug” feature without any addon.

    June 21st, 2011 at 10:18

    1. Admiral Potato

      I second that notion! I have been loving the “Inspect Element” contextual menu option and developer console features being as easily accessible as they are in both Safari and Chrome. I would really love to be able to debug like that on a vanilla copy of FireFox as easily as I can in other browsers, without having to install a plugin.

      June 21st, 2011 at 19:44

  20. Jon Reid

    This is strange. I reloaded the page and had the form pre-filled with Marek’s details?

    June 21st, 2011 at 11:13

    1. Steve

      Same thing happened to me! WTF.

      June 22nd, 2011 at 07:27

  21. Alex


    Great improvements for and ImageData.


    June 21st, 2011 at 11:26

  22. Debbie

    I’m a little leary to upgrade. When I upgraded to Firefox 4 , I found the parental/website controls no longer worked. IF Firefox 5 had parental /website controls that WORK, I will upgrade. Would like some more info in this area, please. As much as I like firefox, I have thought about switching to another browser for parental controls.

    June 21st, 2011 at 17:16

  23. Amith

    Thanks guys. Best of luck in your future endeavors.

    June 21st, 2011 at 17:46

  24. Mark

    Been using the FF 5 beta very stable FF 4 was not I really like this version.

    June 21st, 2011 at 19:04

  25. Gaurav M

    I was expecting to be there.. but not that fast! tremedousily surprised.

    June 21st, 2011 at 23:29

  26. saurabh kumar

    Great work guys!

    June 21st, 2011 at 23:45

  27. ion

    I also sent a feedback to Mozilla:
    This really should have been FF 4.0.2 or FF 4.1 … it’s by no way FF 5.0. There’s no reason to announce a major version if there are no major improvements !

    Chrome is doing this, now Firefox as well.
    I think I’ll switch to Opera after being a loyal Firefox fan since 1.0 !

    June 22nd, 2011 at 01:35

  28. CJ Spencer

    Lovely to see the advancements in CSS3 guys! Great job!

    June 22nd, 2011 at 02:45

  29. Weboide

    Great work!!!

    June 22nd, 2011 at 05:02

  30. Teodor Sandu

    +1 to Broken Skeleton above… great work Mozilla, but a Major release so soon? This may continue for a little while, but unfortunately after 3-4 major upgrades in the next few months a lot of users will get bored of upgrading.

    Furthermore, a Major release is something like “Ok, we admit our browser sucked at some points, so we made it better and it’s not that lame Firefox X any more, but the new, hot and sexy Firefox X+1 now!”. Thus, there’s nothing sexy about Firefox 10 appearing at the end of this year, it just means 6 failures in a very short time. This from the browser with the all-time least failures (compared to all other major browsers with a respectable age – to rule out Chrome which is just a kid, relatively speaking).

    The prospect of seeing so many Firefox major releases in such a short time makes me sad.

    June 22nd, 2011 at 06:48

  31. greg

    Just loved the smooth update procedure from 4.01 to 5.0

    June 22nd, 2011 at 07:15

  32. Christian Sciberras

    Great work? Great work???

    I ditched Firefox 4 at its launch date because it was so buggy; hidden downloads, half of Firebug’s functionality GONE.
    Not to mention they broke existing standards that has been working without a hitch since IE6.

    Now we’re supposed to embrace Ff5 why exactly? It’s even more buggy, contains even more experimental features and drawing-board standards, and it DAMN WORKS LESS THAN v3.6!!

    June 22nd, 2011 at 07:24

  33. Mark Johnson

    Do we still have to use custom HTTP headers to determine plug-ins, instead of just using the user agent parts like BEFORE 4.0? I don’t care about all that other stuff.

    June 22nd, 2011 at 07:25

  34. Christian Sciberras

    Oh and to add to my earlier comment, Firefox has tripled its memory leaks. That’s right folks, they’ve slowly tamed leaks for a while, but now they’re biting back, harder.
    After a while, Firefox 4 takes up to 700mb for 4 tabs. The plugins I use can be counted on one hand, and there aren’t any toolbars/bookmarks whatsoever.

    June 22nd, 2011 at 07:28

  35. Max Zhao

    That’s fast. Have you solved the efficiency problem yet? On my windows box firefox 4 still hangs occasionally and is a grade slower than Chrome.

    June 22nd, 2011 at 07:28

  36. bearmos

    Why the major rev, isn’t this a minor release? I’m all for rapid releases, but just because there’s a “release” every few months doesn’t meant that it needs to be major. This new approach will serious hamper the efforts of add-on developers, since on of the indications of a ‘major’ release is that it breaks things. Is there a place to discuss this new approach to releases further? I’m very surprised.

    June 22nd, 2011 at 07:54

  37. dean

    Gotta love Agile

    June 22nd, 2011 at 08:06

  38. Harry

    So what’s the big deal? 3.6.17 is still giving me everything I need, just where I expect it to be, just how I’m used to seeing it. Dunno, but “major” versions of most any software tend to make me nervous…


    June 22nd, 2011 at 08:37

  39. Mike

    Sounds like you guys like that cake from ms way too much.

    June 22nd, 2011 at 08:38

  40. Tim Keating

    Blah. I despise Chrome’s strategy for revving major versions and it’s not an improvement for FF, either.

    Fast iteration and frequent releases? Great! Changing the major version number every 6 weeks “just cause”? Puke.

    June 22nd, 2011 at 09:01

  41. xLone

    Three months != six weeks. I think you already failed on that part. And I agree with many of the other posters, this should be 4.1, not 5.0. You made no new enhancements to the product, only bug fixes and compliance changes.

    June 22nd, 2011 at 10:36

  42. Oliver

    Does this version also accumulate gigabytes of memory?

    June 22nd, 2011 at 10:52

  43. John

    If Chrome jumped off the Empire State Building would you? Sure seems like Firefox has answered that with a resounding Yes!

    June 22nd, 2011 at 11:59

  44. Aldonio

    I’m not really excited and really dislike that major version development cycle :/

    I agree with releasing versions each 6 weeks, but not as major versions… for me Firefox 5 is just Firefox 4.1

    June 22nd, 2011 at 12:20

  45. John from Zombie Processus

    Great release guys, keep up the good work!

    June 22nd, 2011 at 13:45

  46. Daniel

    Nice! One thing that wasn’t mentioned was whether the issue of memory leaks was fixed in this release, or if it will be more of a priority in a later release. That’s why at home I’m still running 3.6 – since I upgraded to 4 at work, I noticed Firefox caused quite a hit on system performance, with RAM usage steadily increasing to well over the 1GB mark.

    June 22nd, 2011 at 14:53

    1. Nanashi

      As far as I can see, at the moment it’s only taking about 300MB. I don’t know if it’ll change after being on for hours, but that remains to see.

      June 22nd, 2011 at 17:47

  47. Dennis V

    I can’t wait to start taking advantage of these new features. Appreciate the hard work.

    Everyone else; I believe Firefox 5 fits perfect and all other major updates from now will follow as Firefox 5.3 or related to a subversion. This was a big jump but I agree since its a milestone for Mozilla which can now give us an option to be part of beta testing quicker.

    Nevertheless been a fan from the start and will continue to be just that with every update that never stops surprising me.

    Firefox > chrome

    June 22nd, 2011 at 15:04

  48. Todd Fox

    I don’t mind the updates so long as nothing breaks and I don’t have to keep being prompted for them. That is where Chrome wins my favor. I’ve installed it only once and have seen 7 versions filter through seamlessly. Since it’s always updating itself, I don’t have to keep 3 versions of it on my PC to test layout.

    June 22nd, 2011 at 17:01

    1. Christian Sciberras

      Well, here’s the scoop, features start breaking up ever since they wrote v3.5, including 4 and 5…

      June 23rd, 2011 at 07:19

  49. Kabindra Bakey

    Firefox comes ahead once more in rails…

    June 22nd, 2011 at 22:45

  50. Tameem Zaaiter

    Wooooooooow !!!
    I can’t believe this , the 4 version is still fresh ! I think this is a slap at other browser manufacturers faces KEEP IT UP GUYS.

    June 23rd, 2011 at 08:41

  51. Bill Theod

    Everything’s fine with CSS3 stuff but I wonder, when are you going to make Firefox stable? It crashes all the time (some times it lasts more than a minute or two). It takes more than one Gb of my PC’s ram and 30% CPU!
    Firefox rapes our PCs!!!
    I definitely prefer Chrome where I can use almost the same addons without any crashes. If I have to use Firefox I must downgrade to version 3.x (not so many crashes).
    I know you’ll say that maybe it’s some addons that cause the problem and I’ll answer you: give me a reason to use Firefox except the addons flexibility.

    June 23rd, 2011 at 09:08

    1. louisremi

      We do not want our users to stop using addons at all. But we encourage them to try disabling all addons to see if it solves their performance problems.
      In the end, we want users to be able to report valuable information when they encounter problems with Firefox.

      June 24th, 2011 at 09:07

      1. Bill Theod

        Users all over the world reporting problems like this almost every day. I disabled the addons but firefox was unstable again. And every new release is worst than the old ones.
        I was a big Firefox fun but the fact that you don’t do anything to solve these issues makes me to put it in the same place with ie (garbages).
        The only reason I have it installed in my PC is that I have to check with every browser every site I design…

        June 25th, 2011 at 02:31

  52. Paul

    I’ve been a loyal Firefox supporter for years, but version 4 had clunky bits that literally forced me to use Chrome because FF simply stopped working. Now you say that a ‘major ‘ release is every 6 weeks! In truth, they are minor releases, and breaking convention and being non-standard in your release numbering is just the type of arrogance and spin that caused people to leave IE and move to FF! Get with the plan guys! Use standards EVERYWHERE. This is version 4.1!

    June 23rd, 2011 at 15:41

    1. louisremi

      As browser vendors switch to a rapid release cycle (like Chrome and Firefox have done), version numbers will matter less and less.
      What matters is our ability to deliver new features and improvements faster to our users.

      June 24th, 2011 at 09:11

      1. Paul

        What matters to this user isn’t new features faster and faster, but old features that we use everyday continuing to work, and new features added reliably. Version 4 had problems and I couldn’t revert back to version 3. So I had to install Chrome just to do a few tasks I needed done. Version numbers DO matter, in a suttle way.

        June 24th, 2011 at 16:45

      2. Big Red

        I’m going to delete firefox. It is total crap. It goes down 20-30- times a day. The addons don’t work worth a shit anymore. RDR is a joke.louisremi you are a liar IMHO! Keep up the bullshit and nobody will be using your totally crappy browser anymore. You ought to call it Sludgefox!

        August 17th, 2011 at 10:56

  53. Don

    One of my key web applications and add-ons, a bibliographic database, just managed to release a version compatible with 4.0 this week. Now, I see that the add-on manager says it will not work with 5.0. Is this going to happen every six weeks? Too much. Guess its time to see which other browser I can use. Or, uninstall 4.0 and go back to 3.whatever (which I have on all my other computers). What a mess you’ve made of this. Ugh.

    June 23rd, 2011 at 20:26

    1. louisremi

      I guess you are talking about Zotero, which is already compatible with Firefox 5, yay!
      On the + side, more frequent release means less backward incompatible API changes between 2 releases.
      For most addons and most future Firefox release, updating an addon will just be a matter of updating the version string in a config file.

      June 24th, 2011 at 09:14

      1. voloch

        All versions after 3.0.x are too bloated and greedy. Even without any addons or plugins turned on! They consume much more CPU time, memory. One reason I do not use IE is its high CPU usage in certain situations. Now, Firefox is going to absolutely maximum in this. But it will have rapid versions change. So inspiring! I suppose users need no such an “improvements”. I’m still using FF 3.0.19. This is, I see, the highest version of Firefox i’ll use. Maybe Firefox 127… :D
        (Opera since v10 has changed their browser even worse, so that don’t be afraid :D)

        June 26th, 2011 at 11:25

        1. louisremi

          If you find pages where Firefox uses more CPU than usual, you should file a bug on
          You can find a good tutorial here:

          June 27th, 2011 at 05:58

  54. DazzaJ

    Unfortunately it still seems much slower that Chrome and has issues with addons.
    It basically is just version 4 with a couple of tweeks.
    It still falls well short in the HTML 5 tests compared to chrome as well as the java tests.
    I think Mozilla seem too intent on copying their rivals and upgrading version numbers than actual performance or features.
    Firefox has fallen to my 2nd browser of choice since release of version 4, Chrome takes the lead.

    June 24th, 2011 at 04:16

  55. jswidget

    Firefox 4.01, which should be called finally fixed the annoying out of canvas put/getImageData issue. Great thanks, no walk-around needed

    June 24th, 2011 at 05:41

  56. Serp

    If Chrome figures out to put the file menu back, including a favorites bar and easy options setting, plus manages to figure out how to give better extension support (mostly for Ad Block Plus) then Firefox is pretty much finished.

    The Firefox team seems intent on just copying Chrome but being worse at everything. So while Chrome will improve, Firefox will just get worse because it will always be a step behind.

    3.6 was the last great Firefox version. 4 is pointless but Chrome still lags a little behind in certain things that for me are enough to use Firefox. At least 5 didn’t break things from 4, just don’t know really what the improvements were. Just call it 4.1 and be done with it.

    June 24th, 2011 at 05:51

  57. Debbie

    Question: How can I downgrade to firefox 3??? I liked that version much better than 4 or 5, mostly because I can get PARENTAL CONTROLS. Thinking of switching to another version. Chrome have parental controls?

    June 24th, 2011 at 10:10

  58. Carmen Brodeur

    Now my favorite addon of all time – nodo follow won’t work! Not compatible with 5.0. What should I use instead? or should I downgrade to lower version of firefox?

    June 24th, 2011 at 10:44

  59. Rune Jensen

    I do not understand all those who have problems with firefox craqshing? I haven’t had a crash since 3.5 or so.. And this is nothing different. You choose you addons and extensions wisely, then you will not crash!

    Good work, though I agree that 5.0 is a strange number. I gess we will all get used to it though.

    June 24th, 2011 at 11:49

  60. Webgranth

    I was eagerly waiting for the release of the new version of the Firefox.

    June 24th, 2011 at 21:55

  61. Ryan

    To all the people complaining about crashes. Firefox IS NOT unstable. What makes it unstable is your user profile. Over time, and especially over multiple versions of Firefox, the profile accumulates tons of settings, add-ons, and other bloat that eventually causes conflicts and bugs that cause Firefox to crash. If you want to see how fast, secure, and stable Firefox really is, create a new profile.

    June 25th, 2011 at 05:23

    1. But How?

      How do I create a new profile? What’s entailed in this?

      June 26th, 2011 at 20:41

      1. Ryan

        You’ll lose all your personal data–bookmarks, history, passwords, extensions–but if you’re using Firefox Sync, the only thing lost will be extensions.

        June 27th, 2011 at 07:06

    2. Big Red

      Blame the user! What bs! Quit using sludgefox. it is crap!

      August 17th, 2011 at 10:58

  62. Alexander Gelbukh

    “What makes it unstable is your user profile.” In other words, FireFox is OK, what makes it so bad as it is is the fact that we (still) try to use it. Unless you use it, it’s perfect!

    June 25th, 2011 at 06:30

  63. Anupam Gangopadhyay

    We need Firefox5 for Samsung Bada Operating System. Is it Possible?

    June 25th, 2011 at 08:01

    1. louisremi

      We are currently focusing on Firefox Mobile for Android, but follow other mobile environments closely.

      June 27th, 2011 at 06:01

  64. obiwahn

    Why are you all complaining about the version numbers?
    As long as they strictly monotonic increasing i don’t care about the distance^^

    June 25th, 2011 at 09:27

  65. Andres Riofrio

    It’s just a number.

    It breaks extensions now, but I think developers will learn to disable the compatibility check (

    I’m happy. Some extensions were disabled, but this is temporary. On my Ubuntu box, Firefox gets updated automatically, but on other systems, it’d be nice if it did.

    I understand there are companies that would not like their browsers to be updated automatically. This should be easily changeable at installation time or with a user preference.

    June 25th, 2011 at 15:01

  66. Piglet

    I find Firefox is just becoming a rather ugly version of Chrome.

    June 26th, 2011 at 10:28

  67. Snapafun

    Updated to FF5 and now I have some real issues. I came to FF years ago and have been faithful – TILL NOW.
    FF5 is slower and the number of broken addons is excessive.

    Your comment earlier “We do not want our users to stop using addons at all” is laughable at this time because more than half of my regular addons fail even though most of them claim to be compatible with FF5.

    FF4.0.1 solved issues and I personally found it stable. FF5 is so stable it will sit there and do nothing for minutes at a time. And when I choose to use the feedback feature – that dies as well.

    Now I need to look elsewhere because I choose to do some work these days, not sit here all day trying to get things to work.

    Here’s an example – Fast Dial has always followed the updates – today it installs, I get to see TWO entries in the right click menu, the options don’t stick and I’ve lost visual access to my library of links. Think it’s the addon? Try loading a new tab and explain why the url doesn’t render as “about:blank” – something needed for such addons to work. The url and page simply open blank – nothing – just blank. Something in FF5 has shut active events for this down??? I’m not a coder though I’ve seen many different events over the years and this smacks of SHUT DOWN just as things did with WinMe at the turn of the century.

    Me thinks you have gone backwards – FF has become a heavy app that sucks resources and takes its’ time getting things done. Feels like a windows app more and more.

    I appreciate that many hours have been voluntarily put to FF – it’s just that you focus has become tunneled to suit your purpose and seeing the users requirements has no place with you anymore. For a long time now the resource issue has been out there and if anything it has just got worse.

    Backward compatibility is not even considered these days and if we have a machine more than a year or so old – tough!

    Bad user satisfaction and I fear many have migrated not to return. Shame, I really do like FF BUT I NEED TO GET SOME WORK DONE!

    June 27th, 2011 at 05:04

  68. erica

    after updating to 5.0 i got a virus as mcafee was disabled for the update. i now can not access the internet via firefox due to ‘proxy server error’. i am a computer novice and have no idea how to fix this…..can anyone help me?!!!!

    June 27th, 2011 at 18:57

  69. Arsimael

    Sorious Guys, I’m using Firefox since it’s name changed to “Firebird”, but your current “developing” makes me looking for alternative browsers.

    I don’t wan’t to get mad every three month because my Addons are not working because theres a new bugfix which has to be delivered through a new Majorversion which deactivates all my addons beause they’re “not compartible”.

    Sorry Guys. It was a nice time. But I need a Browser which does not fuck up all my addons and options because the Developers think they need a Number with two digits at the end of the name. And Firefox is nearly unusable through this “We-need-a-higher-Version-to-be-as-cool-as-opera-or-chrome”.

    It would be very less troublesome to write a 4.1 at the end of the name nstead a 5…

    June 28th, 2011 at 06:54

    1. R-J

      pffff, version number wise only opera is really cool, they have the history to deserve it. ps, nice document:

      Firefox 3.8, it isn’t my main browser, but I have to say I have little problem with it. The interface changes following Opera and Chrome leave me more screen-real-estate on these modern-age wide-screens.

      And now more standards support. This is an exciting time with the implementation of HTML5, css3 and the race to be the fastest. And FF is looking good in it. Not the top, but it is an honest browser that I trust will pull itself back to it fast enough.
      You can’t expect fast development to go without hiccups.

      Where Google has money and some great minds and Opera has people that live for the web, open-source is about communities. People, send your bug-reports and give your support. You don’t have to be a programmer to contribute.

      Anyway, (a late) congrats on the new release, lovin’ it!

      August 10th, 2011 at 16:29

  70. haroldandresme

    Older version of FF is BETTER the latest versions.. Problems should be fixed asap. the new version of IE is BETTER the FF new version., :( I want to use FF., but it always crushed.

    June 28th, 2011 at 19:20

  71. Snapafun

    Got my Fast Dial Back for now… had keep my download of version 4 so went ahead and re-installed it – hello Fast Dial – welcome back. now to see if I can still download version 4.0.1.

    If anyone here gets Fast Dial reliable in FF5 – please post back here so I can look at trying FF5 again. TIA

    June 29th, 2011 at 02:32

  72. Snapafun

    Update: Anyone else needing to get back to FF4.0.1 can get it here.

    June 29th, 2011 at 03:04

  73. josh

    I think people are more bugged by the name then any thing else. I remember when 3.0 came out it meant something to finally be out of 2.x and there was real changes then again with 4.0 but with 5.0 it feels to quick and falls externally short of a title as 5.0 from a great company and is a smack in the face of fans from the 2.x era and I’m sure fans from dating back to the 1.x era feel a punch to the gut when you say a minor update and almost no ui update a full fledge new series of firefox. At first I thought I was being attacked by a hacker when it said 5.0. Then after it updated to me it still felt like 4.0. When I hear of 5.0 I think of a fire fox that is 300x faster then 4.0 has a new loading system. smashes html5 standers so much so it feels like its asking for html6. Maybe even have thunderbird built right in ff5. Has Smart Voice so you can talk to fire fox.Use a web cam so firefox can see you and understand you when you point at some thing. Thats my idea of ff5 another break through in web browser technology but hey thats just a loyal fans idea of ff5. Names matter more then you think. After all would you want an Olympic mettle or a trophie from a little league after all theres just names there the same sport but at different levels. Names are earned.

    July 2nd, 2011 at 13:10

  74. Snapafun

    Basically, I got Fast Dial back by downloading the beta version. Even this suggests that there’s nothing wrong with Fast Dial, just that things have been taken out of the hands of developers especially in FF5 so they are frustrated somewhat. Regardless, you can get Fast Dial back with FF5 by going to this url: Enjoy.

    July 3rd, 2011 at 04:17

  75. obiwahn

    As said – I don’t care about the funny numbers:) But maybe you want to introduce some kind of version number or something like the component object model for the plugin interface. Not working plugins (because of version number breakage) are in fact a annoyance – ok – i have no problem fixing that .. but some other people here seem to fail:P

    July 4th, 2011 at 03:03

  76. rayblan

    Why can’t the google toolbar be made compatible with so that I can download the upgrade?

    July 5th, 2011 at 01:20

  77. snoopy

    I assume you haven’t dropped support for @fontface? Tried a reinstall without plugins but still doesn’t work. Any suggestions? I’m using the Paul Irish ‘bulletproof’ method at the moment.

    July 7th, 2011 at 04:18

    1. louisremi

      We still and will likely always support @fontface.
      Please use forums for support requests not related to this article :-)

      July 7th, 2011 at 05:36

  78. anand

    I have firefox 5 on Solaris 10 (x86) and none of the youtube flash videos are working. I could view some flash videos from a site though. Strangely the flash settings manager content isn’t visible now. Any idea?

    July 7th, 2011 at 14:37

    1. anand

      BTW, I have flash 10.3 r181

      July 7th, 2011 at 14:38

  79. Rob

    What a lot of extraordinary negativity! I’m finding FF better than ever.
    FF4.0.1 was better than FF4 which was better than 3.6, though I took a few days to appreciate & figure out the new UI.
    FF5 has been the best release, so much so that I’ve actually started running Aurora 7.0.2 Alpha without much issue.. AND guess what my most important Add Ons work! NoScript, WoT & Adblock Plus (HashColouredTabs+ to).
    Everything else is just nice to have…
    I USED to have crashes under Win & Linux, with FF 3.x regular, but they’re few and far between since FF4.

    July 10th, 2011 at 06:26

  80. laz123

    I’ve always been a Firefox fan, since the 2.x version. Lately I think Google Chrome is a lot better in many ways, so… I’m starting to prefer it over Firefox. It’s sad to see such a disrespetful marketing strategy followed by Firefox by naming the current version 5.0, as many of you have already pointed out. Extension support isn’t great and it still requires a browser restart. Resource usage is incredibly high.
    I need to be re-convinced that firefox is the best browser out there, i hope they’re gonna do smth about it.

    July 10th, 2011 at 11:21

  81. Seth

    extensions need to abandon “maxversion” entirely as rapid release equals rapidly broken extensions

    firefox is (was?) popular because of its extensions

    adblocking is a security necessity for interweb use for users incapable of not-using the wrong local security context

    July 12th, 2011 at 15:53

  82. Gemma

    Don’t know why people are complaining to FF about the crashes and freezes. Do something about your PCs.

    I use a £300 crappy laptop from Compaq, and FF5 has not crashed on me. The worse it does is to freeze for 30 seconds sometimes, and that’s because I have 3GB RAM with TweetDeck, Chrome, FF, Dreamweaver, etc all open, and usually have multiple tabs and addons/extensions in Chrome/FF.

    The crashes are not down to FF. It’s down to your PC hardware setup/config, and possibly the OS you use.

    August 15th, 2011 at 08:01

  83. Peter

    I too felt the new number (5) was some scam by a hacker, haha. Firefox saddens me because it has abandoned it’s niche in the market. For people who want a flashy browser with no ability to control, just to surf, they can use Chrome. For people who want a powerful but resource light, highly usable browser, they can use FF. But now there is no option for users of the second category, other than using older versions of FF. I agree with the consensus that FF 3.x was the last great FireFox.

    Just as an example of how great the previous versions of FF were, I use FF, the last version before 3, on a 400MHz Win 98SE machine! This version was the modern version in the fairly recent year of 2008. It was meant to take advantage of multi-gigahertz machines running Vista, and yet is resource light enough to be a great browser on this vintage machine from 1999.

    September 1st, 2011 at 13:35

  84. Cookie Monster

    OS is not a case. Firefox turned into complete crap in OSX as well as Ubuntu. Don’t wanna repeat all the complaints and issues, but I had most of them on multiple machines with multiple configurations starting from FF 3.x

    Maybe it’s my ‘user profile’ thing, I don’t give a shit anymore. Years of struggle and hope turned to be because of me deteriorating the situation, simply by casual browsing. I don’t wanna do anything with it, I’m just migrating to Safari – the best fully-functional browser so far, unfortunately not available in other OSs. Thankfully, my bookmarks have always been in the cloud.

    Firefox’s de-evolution and Mozilla staff’s arrogance sadly remind me recent downfall of Nokia when they started introducing creepier and creepier crap instead of new products and versions.

    September 7th, 2011 at 18:43

  85. some random user

    @Cookie Monster:
    Where exactly was your struggle? Ok its a pitty that you had to learn how to use a new browser:) Have fun with libwebkit:P maybe you want to google for “libwebkit safari CVE”.

    And i am sure as hell that you did not contribute in any way still you insult people without having the slightes idea why some decisions have been made. having to deal with dumb, nonconstructive ppl like you enrages me.

    The mozilla guys give us a good and free browser you do not have to use it. and you have no right to act as if you payed for it so you can tell them how it has to look and feel.

    I have no crashes at all and the browsing seems overall better. Older versions work better on my old computers. But you surely do not complain about windows7 not running on your loved p75.

    September 10th, 2011 at 02:54

  86. Rob

    @random user : Hear, hear!!

    FF5 wasn’t a problem in the Linux I use. If the ppl who sound off, spent 1/4 of the time looking for their own mistakes, they’d likely have smooth running system. Course just they get more of a kick out of ranting!

    September 21st, 2011 at 06:47

  87. Web Dev

    Thanx to Firefox dev team, Firefox is getting worse and worse. What they have done with setTimeout and setInterval functions is nonsense

    October 12th, 2011 at 05:26

  88. F. Dotzler

    Firefox 17 already? Just kidding. It’s arrogance and playing with numbers and a love for marketing first instead of quality first. It’s also another excuse for the “developers” to change things for no reason and break UI familiarity and “play” around with the software instead of keeping things consistent and efficient. Just because software can be changed doesn’t mean it should be. Stop chasing after the latest fancy “new” web “thing” and make the product consistent and do it right the first time instead of causing millions of people to have to “relearn” the “new” functionality and UI layout every 10 months. You firefox apologists are not listening to sound logic on this thread and the fact that reliability is way more important than fanciness and “features.”

    October 29th, 2011 at 11:47

  89. jeuxdotnet

    Thanx to Firefox dev team, Firefox is getting worse and worse. What they have done with setTimeout and setInterval functions is nonsense

    November 1st, 2011 at 10:27

  90. Gary Brown

    Been with FF since the beginning and have finally been forced to upgrade to FF12 for OSX. It is utter crap. Refuses to load new tabs about 50% of the time, slow and all my add- ons are disabled. Looking for a new browser as I can’t go back to the previous version.

    April 25th, 2012 at 02:09

    1. Jean-Yves Perrier

      You should ask for help on the support site: . They will be able to help you fix the problems and find alternative for orphaned extensions.

      Also note that your add-ons will also not work in another browser: in both case you will have to find replacement. (I assume you were using Fx 3.6 and not Fx 5 like where you are posting).

      You’re lucky we noticed your comment. Usually posting a comment in a random post doesn’t help you match in getting help.

      April 25th, 2012 at 17:00

Comments are closed for this article.