We're sorry to hear that Firefox is crashing when you open it. Please do the following to give us crash IDs that will help us understand more about the crash.

1. (OS X 10.6 or previous) Click the Finder icon in the dock. Your home folder will be selected. In the right side of the window, click the Library folder to open it. Then open the "Application Support" folder, the "Firefox" folder, the "Crash Reports" folder and finally the "submitted" folder.
   (OS X 10.7 or above) Click the Finder icon in the dock. On the menu bar, click the Go menu, hold down the option or alt key and select Library. A window will open containing your Library folder. Then open the "Application Support" folder, the "Firefox" folder, the "Crash Reports" folder and finally the "submitted" folder.
2. Open the 5 most recent files with a text editor and copy the IDs.
3. Paste each ID with bp- into the reply window on the forums.

Thanks in advance!

You can find more information and troubleshooting steps in the Troubleshoot Firefox crashes (closing or quitting unexpectedly) article.

Thank you for your reply. In the meantime, I have found that there are deeper logs on crash-stats.mozilla.com if I am lucky and can get into about:crashes and copy the link. From what I can understand, it seems to be crashing always on this thread:

nsNativeThemeCocoa::DrawWidgetBackground(nsRenderingContext*, nsIFrame*, unsigned char, nsRect const&, nsRect const&)

Following are my crashlog IDs:

bp-0bf11074-bf41-49b7-90c4-8e3e72150513 bp-8c0190c0-ca5f-4f2f-9b45-15eb92150513 bp-e87bb232-fa51-499a-9ec9-35f902150513 bp-2a1271e8-37f3-4e1e-aa93-9938b2150514

Thanks for your help!

I will leave it to those who understand Mac s to give you proper assistance, but one potential: longshot |troubleshooting step |workaround: Try changing your scale factor back to the default 1:0

It seems likely the crashes are somehow related to your Mac display & theme, and probably something that is not common and not default.

I make that suggestion as I see CorUI involvement in the crashing thread and it appears that is turned off in the default resolution. It is probably also worth considering the Mac themes and reverting them to defaults.

• http://www.theregister.co.uk/2009/01/12/mac_secrets_coreui/

Some folks have reported that CoreUI isn't used at all in Leopard, unless you change the scale factor from its default value of 1.0, but this is simplistic. By default, CoreUI is used for drawing a number of user interface elements in Leopard.

OK I realise that is the wrong OS X version, & Yosemite may not even now have a setting "scale factor" but experimenting with resolution etc may be a better workaround that Windows in a VM, and may give other clues as to methods of preventing the crashes.

The crash signature you see is very rare, possibly unique to you !

• https://crash-stats.mozilla.com/report/list?product=Firefox&signature=CoreUI%400x20018

John99 thanks for your investigation, it inspired me to try some adjustments - first was to avoid external display as I use it always and has not tried to run firefox without, but no success.

As for themes and scaling factor: afaik there are no themes for OS X and scale factor is something obsolete from my googling attempts. As I mentioned, this is nearly clean installation with no special apllications installed and no third party drivers or anything else I would suspect. Also I tried to use new user profile where even system settings were set to default and crashing is the same.

Also an idea crossed my mind - when the problem is so rare/unique, it might be some hardware malfunction (possibly memory). But everything else is working fine (and this is my working machine so I use it whole day and quite heavily).

So I'm still quite desperate, but anyways I really appreciate your interest!

Your crash ids all had the same signature. Do you have other recent crash ids with differing signatures ?

You mentioned reinstalling Firefox did you try a clean reinstall, leaving the Firefox profile but deleting all the program files.

Also have you tried the clean install with a clean Firefox profile. (Temporarily rename "profiles.ini'" will create clean profile. ). I have not got links,using phone for this post.

Jonh99: I am not really sure what signature consist of, so I just tried to evoke few more crashes in different situations (typing into adress bar, opening preferences, opening addons tab) and the signature seems to be still the same.

bp-8e6a3ab1-6e64-4159-b184-59a7f2150515 bp-0af75efb-3eb8-4e08-9a67-74d412150515 bp-70b00c37-e1a7-4a91-8058-4cdf92150515

As for clean install: in OS X, I suppose the only thing to completely uninstall Firefox is to move the application to trash (empty it) and remove folders ~/Library/Application Support/Firefox and also (for the paranoia) ~/Library/Application Support/Mozilla. I did it multiple times this way with even different versions.

I even tried to create new user in OS X with no firefox installed and install it as new user but it is still the same.

It seems that only possibly working solution would be to clean install OS X, but it is quite drastic for me...

By the way, I noticed that also Komodo Edit is crashing quite often (it is mostly possible to work with, but some actions or some areas in preferences cause crash). As it is also based on XUL, I tried to find out if the reason of crashes is the same, but Komodo crash reports works a little different and link to the report throws not available: http://crash-reports.komodo.activestate.com/submit/report/index/fe80e2f6-fad4-11e4-a054-080027a7c3ca

Still I find it interesting fact....

Give it a couple of days to see if anyone else comes up with answers, if not post back and I will see if I can find anyone else to help.

The crash signatures are the same in the new CrashIDs . ( The CrashID Signature is shown in the heading and signature field of the reports.)

Using another OS account will ensure Firefox has a new profile Your deletion of all Firefox related files is a clean reinstall. The related help article links are

• Firefox keeps crashing at startup_try-a-clean-install
• Profile Manager - Create, remove or switch Firefox profiles_creating-a-profile
• And my suggestion about renaming profiles.ini

... If you delete the profiles.ini file, a new default profile will be created the next time you start the application and a new profiles.ini file will be generated that references the new profile.  ...  

For forum cross referencing purposes

• Reports for your CrashIDs
  bp-0bf11074-bf41-49b7-90c4-8e3e72150513
  bp-8e6a3ab1-6e64-4159-b184-59a7f2150515
• Crash Signature: CoreUI@0x20018

So I gave it couple of days and seems nobody comes up with new ideas... In the meantime, I have changed RAM for new one and the problem persists so I would not suspect faulty memory.

If there is somebody with deep understanding of OS X and might try to help me find out what is different on my system, I would really appreciate it.

OK I have tried one thing I haven't yet and it seems to solve the problem: restart OS X in safe boot.

I don't know why this helped, first I thought it will only help to isolate the origin of problem to things that safe boot solves and that doesn't solve clear user profile (excluding 3rd party kernel extensions, clearing font cache and disabling non system fonts), but the funny thing is, that not only in safe boot, but also after booting normally again, firefox seems to be stable.

Thanks again guys for the help and I can happily use my firefox now :)