Available languages: Italiano,

Reporting Bugs

Summary (or tl;dr version)

Here is a brief summary of the bug reporting procedure:

  1. Consider whether a support request would be more appropriate than a bug report

  2. Try running in safe mode or disabling extensions

    • If disabling extensions resolves the issue, then please don't report a bug against the application (although if the problematic extension is provided by Ubuntu, please do report a bug against that extension)
  3. If you're sure that your problem is a genuine application bug, please check if the bug has already been reported

  4. If your bug hasn't been reported then you should report a new bug. However, please run through this simple checklist before doing so:
  5. Now you can report a bug! When doing so, please keep in mind the following points:


You can help Ubuntu developers improve Firefox and Thunderbird by providing them with useful bug reports. This means that you should provide as much information as possible to describe the bug (please see How to report Bugs)

You may find that you need to use the Terminal for some of these commands. If you are not sure how to use a terminal, please see the Terminal Guide for a basic introduction.

We get a lot of Firefox bug reports from Ubuntu users and a lot of these don't contain sufficient useful information to progress them further, or sometimes even understand what problem the user is reporting. Please understand that we don't have the manpower available to spend time on every bug report to continually ask reporters for information that could be provided up-front. To increase the chances that your bug report attracts the attention of a developer, you must follow these guidelines. A developer will ask you for the required information that you didn't provide, so following these guidelines will save time for the person who looks at your bug report.

Consider whether a support request would be more appropriate

Please only report a bug if you have identified an actual software defect in Firefox or Thunderbird. A defect is where some piece of functionality is broken, or clearly does not behave as expected.

If you require help with using either application, or you have a question or any other problem that you would like help to resolve, then there are more appropriate resources that you can use in these cases (rather than reporting a bug):

If you are unsure whether your problem should be reported as a bug, then please ask a question in one of the above mentioned sites. Alternatively, if you would like help in your native language, you could try using the support forum of your local Ubuntu community. To find this, and other ways to get in touch with your local Ubuntu community, please visit http://loco.ubuntu.com/.

See also http://www.ubuntu.com/community/report-problem.

Try running in safe mode

Some problems are caused by third-party themes, addons and plugins, or customization of hidden preferences in about:config. These customizations can be disabled temporarily by running Firefox or Thunderbird in safe mode.

To run Firefox in safe mode, ensure that you have closed all instances of Firefox, press Alt+F2 and run firefox -safe-mode.

To run Thunderbird in safe mode, ensure that you have closed all Thunderbird windows, press Alt+F2 and run thunderbird -safe-mode.

If the problem goes away in safe mode then it is caused by one of your addons or customizations. In this case, please do not report the bug against Firefox or Thunderbird in Ubuntu. If you have time, you could try to isolate which addon or customization causes your problem, and contact the developer of the problematic addon.

Link to Mozilla Documentation

Check if the bug has already been reported

Please try to make the effort to check if your bug has already been reported. We appreciate that sometimes it is difficult to know what to search for, and it may be difficult to spot duplicates in the presence of so many other bug reports.

Launchpad has a facility to search the bug database. You can search Launchpad directly from the following links:

You may have better luck by using Google directly. If you search from Google, try prefixing your search term with https://bugs.launchpad.net:

Use Apport

All Firefox and Thunderbird bugs must be submitted with Apport (unless there is another problem which prevents you from using Apport).

For Firefox, please press Alt+F2 and run ubuntu-bug firefox.

For Thunderbird, please press Alt+F2 and run ubuntu-bug thunderbird.

Using Apport attaches a lot of useful information automatically, and saves time by answering a lot of common questions that developers and bug triagers would normally need to ask. Please do not submit Firefox or Thunderbird bugs using the Launchpad interface. Doing so reduces the chances of your bug report receiving attention from a developer, and your bug report may be closed with a comment asking you to resubmit it using Apport. Please remember that a lot of bug triagers are volunteering in their own time, and appreciate bug reporters helping themselves as much as possible.

Be specific

Try to make sure that the developer will be able to reproduce the bug you are seeing. Provide every detail you can regarding the bug, especially an explicit statement of exactly which sequence of user actions are needed to reproduce the bug. Please don't assume that just because you experience a bug, that it will be trivial for other people to reproduce.

Multiple problems

Multiple, unrelated bugs must be reported as separate bugs. Please do not use a single bug report to report or discuss multiple, unrelated bugs. If you do this, then it is highly likely that a developer will close your bug report and ask you to report the problems separately.

Look for your problem on SUMO

Please have a look on http://support.mozilla.org/, to see if anybody else has asked for support for a problem that is similar to your own. You may find that the problem you are facing isn't really a bug, or the problem has already been reported to developers. You may also find a workaround for your problem too.

Is the problem Ubuntu specific?

When reporting a bug, it is often useful to determine whether the problem is specific to Ubuntu builds of Firefox and Thunderbird. In order to determine this, please try to recreate the problem in an official Mozilla build of Firefox or Thunderbird. These can be downloaded from the following locations:

To run these you will need to extract the downloaded tarball. Once you have done this, open a terminal and do the following:

 cd ~/Desktop/firefox # Assuming that you extracted the download to your desktop.

Obviously, for Thunderbird, replace "firefox" with "thunderbird".

If the same problem can be recreated in the official Mozilla build that you downloaded, then you can help Ubuntu developers by reporting your bug in the upstream bug tracker. To do this, please have a read through the upstream bug reporting guidelines.

Problems with a specific website

If a website does not display correctly in Firefox, you must provide the following information where possible:

  • A screenshot clearly showing the problem.
    • Please remember that the problem may not always be obvious to somebody else who isn't familiar with how the website should normally appear. In this case, please describe exactly what is wrong.
    • You probably want to remove personal information from any screenshots.
  • The URL of the page causing the problem (preferably a URL which doesn't require signing in, although we appreciate this is not always possible).

You might be surprised that we do get reports about websites not displaying correctly without any of this information provided.

If you have a problem with a website, please also do the following:

  • Try using the website in another (non-Gecko) browser (eg, Chromium or Epiphany).
    • Please state which other browsers you tested when submitting your report.
  • If the website works correctly in other browsers, please provide a screenshot showing what the website should look like.


Some things to consider

Please don't assume that everybody else will be able to reproduce your crash, just because you experience the issue. All crash reports must be submitted with a complete stacktrace and a description of the steps required to trigger the crash (if it is reproducible). If the problem occurs on a specific website, please also include a URL.

Bug reports which tell us that the application crashes without any other technical information about the crash (ie, a complete stacktrace) are not very useful.

Submitting Crashes to Mozilla

If you are using the release or beta channel, the preferred way to submit crash data is to send it directly to Mozilla when the crash dialog appears. In most cases it isn't necessary to open a bug in Launchpad when you do this, especially if the crash report you submitted is already linked to a bug report in the upstream bug tracker, or the crash is being experienced on non-Ubuntu systems (eg, other Linux distros, or even Windows or Mac OS). If the crash you submit appears to be unique to Ubuntu and it doesn't have a bug open in the upstream Bugzilla (or you just feel that Ubuntu developers need to be made aware of it), then feel free to open a bug in Launchpad. If you think that the crash is occurring due to an addon shipped by Ubuntu, then you should report the bug in Launchpad.

If you do open a bug report in Launchpad, you must provide the crash ID of the crash report you submitted, and please use Apport.

To find the ID's of crash reports that you have submitted, go to Help -> Troubleshooting Information and click on the about:crashes link in the "Application Basics" section. This is applicable to Firefox and Thunderbird.

Note that the Apport hook provided from Firefox and Thunderbird 13 will automatically attach the ID's of crash reports you submitted to Mozilla, so you don't need to look for these manually as long as you submit the bug report using Apport

Run Firefox in a Debugger

If you are using Aurora or Nightly builds (which don't have the crash reporter turned on), then you will need to get a stacktrace manually using gdb. In some cases, a developer may ask you to do this in order to see local stack variables, which aren't visible in the upstream Socorro interface.

To begin, please install gdb

 sudo apt-get install gdb

Then install the necessary debugging symbols.

For Firefox:

 sudo apt-get install firefox-dbg

And Thunderbird:

 sudo apt-get install thunderbird-dbg

These symbols will also be useful in most cases for both Firefox and Thunderbird. Please install them:

 sudo apt-get install libgtk2.0-0-dbg libglib2.0-0-dbg  libx11-6-dbg libpango1.0-0-dbg libc6-dbg

After closing all instances of Firefox, start Firefox from the terminal with the following command:

 firefox -g 2>&1 | tee ~/gdb.txt
 (gdb) handle SIG33 pass nostop noprint
 (gdb) set pagination 0
 (gdb) run
... # run and reproduce crash
 (gdb) bt full
 (gdb) thread apply all backtrace full
 (gdb) info registers
 (gdb) quit
  1. Now ~/gdb.txt will contain the info we need to initially process your crash bug. So, please attach that file to your bug report.

Please use the same steps for Thunderbird, but replacing "firefox" with "thunderbird" instead.

Hangs, or excessive CPU usage

If Firefox or Thunderbird appears to completely lock up, you must provide a stacktrace of the hung process with your bug report. In most cases, hangs are quite random and non-reproducible, so please consider this before reporting a bug without any technical information about the hang.

If it appears to be using excessive CPU, please first try running in safe mode or disabling addons and plugins. If the problem is with Firefox, are you viewing pages with Flash or video content, animated gif's or other animations? Does the problem stop when you no longer view these?

If none of your addons are causing excessive CPU usage, and you're not viewing videos or Flash content, then there are a couple of things you can do to make your bug report more useful. First, please get a stacktrace whilst the process is spinning the CPU. Secondly, it would be great if you could try to use something like sysprof, which is available in the Software Center (see Sysprof, System-wide Performance Profiler for Linux

Some people also run the application in strace when reporting issues with excessive CPU usage. In general, the output of strace is not all that useful when debugging an issue where the process is CPU bound.

Getting a stacktrace of a hung process

Getting a stacktrace of a hung process is quite easy. First, please install gdb and the required debugging symbols as advised in Run Firefox in a Debugger.

If the hang is reproducible, just run Firefox or Thunderbird as described in Run Firefox in a Debugger and get a stacktrace when the application has hung.

If the hang is not reproducible and you want to get a stacktrace of an already hung process, you will need to attach gdb to it. To do this, first run:

 pidof firefox


 pidof thunderbird-bin

...to get the PID of the process. Then do:

 gdb 2>&1 | tee ~/gdb.txt
 (gdb) handle SIG33 pass nostop noprint
 (gdb) set pagination 0
 (gdb) attach <pid>

...now you can get a stacktrace as advised below (assuming the process was hung before attaching gdb)

 (gdb) bt full
 (gdb) thread apply all backtrace full

If you're debugging excessive CPU rather than a hang, please repeat the following steps a few times:

 (gdb) continue
...# now press CTRL+C to interrupt it again
 (gdb) bt full
 (gdb) thread apply all backtrace full


 (gdb) quit

Please remember to attach the resulting file to your bug report.

Check the Error Console

Some bugs may result in unhandled JS exceptions or other error messages being logged to the error console, and these may provide a strong clue as to the cause of a bug. To view these, open the error console from "Tools -> Web Developer -> Error Console", and select "Errors".

Note, you many need to enable the menuitem to access the error console. To do this, open "about:config", and set "devtools.errorconsole.enabled" to "true"

Excessive memory usage

If you are reporting a bug about excessive memory usage, you must copy and paste the contents of "about:memory" in to your bug report, once you have reported this with Apport. Please don't report bugs about memory usage without this information, as it will be the first thing a developer asks for anyway.

In the future, we hope to automate this step.

You can access about:memory in both Firefox and Thunderbird from Help -> Troubleshooting Information (or you could just type it in to the address bar in Firefox if you prefer).

When reporting your bug, please also describe the scenario which triggers the problem. Does it happen on a particular site? If so, please provide a URL. Please also try disabling all of your addons (you will be asked to do this anyway, so you can save other peoples time by doing this when reporting your bug).

Note that debugging memory leaks in Firefox is quite involved. If you're feeling adventurous, please take a look at Debugging memory leaks and Debugging Mozilla with Valgrind

Other specific issues

Problems with menus on systems that use a global menubar

By default, the unity shell shipped in Ubuntu 11.04 and newer displays window menubars in the top panel. Some other desktop environments may also provide similar functionality (there is a plasmoid for KDE which does this).

In these environments, problems with the menus are not always an application bug.

If you experience an issue with the content of the menubar, menus or menuitems (ie, what the actual text says, what the icons display or the state of any radio or check items), then this should be reported as an application bug (against Firefox or Thunderbird). If you experience an issue with actions (ie, what happens when you click on a menuitem or invoke an accelerator key), then this might also be an application bug.

In general, any problem with the view of the menubar, menus or menuitems is normally a bug with the desktop shell instead. Examples of this might include:

  • Alignment of elements in the menu
  • Colour or theming of the menus
  • Menus not responding correctly to events (ie, submenus not opening on mouseover or menuitems not highlighting on mouseover)
  • Menus appearing in the wrong place
  • Menus appearing behind windows
  • Problems with how large menus overflow
  • Menus not hiding when clicking on another area of the screen, or multiple menus appearing at the same time

If you have an issue like any of the above, please don't report a bug against Firefox or Thunderbird. You should report a bug against the particular desktop shell you are using instead (ie, unity).

No context menu available in the global menubar / can't manage bookmarks using the global menubar

When using Unity, there is no context menu in any of the window menus, and the menus do not provide the ability to drag and drop bookmarks to sort them. This is not a bug. Here is an explanation why:

  • The menus are not a bookmark editor. Firefox already has a dedicated tool for managing bookmarks
  • No other application on the default install provides a context menu in its window menus. Not having one in Firefox improves consistency and removes an element of surprise (ie, when you right click on a menu in another application and realize that it invokes the menuitems action rather than showing a context menu)
  • The functionality is not supported by any other components involved with providing the menubar (ie, dbusmenu, unity and even GTK), and so, there isn't any change we could make in Firefox that would add this functionality to the global menubar.

Please don't report this issue as a bug.

Keyboard type-ahead feature does not work with the global menubar

Gecko has a feature that allows you to select bookmark items from a menu with the keyboard, using a type-ahead like feature. Other toolkits lack this feature though, so this won't work with the global menubar. Please don't report this as a bug against Firefox. This is functionality that needs to be added to the toolkit responsible for drawing the menu.

See bug 917753

The "Open with" dialog does not offer a choice of applications

When downloading a file type that Firefox is unable to view, Firefox presents a dialog that gives you the option of saving the file to disk or opening the file with an application installed on your system ("Open With"). However, "Open With" currently only offers the default handler for the particular file type, and the only way to specify an alternative application is to navigate the filesystem.

This is a Firefox limitation that we're already aware of. Please don't report new bugs for this problem.

See Bug 18995

"Secure Connection Failed" errors

If you see a warning with the title "Secure Connection Failed" and the text "The certificate is not trusted because the issuer certificate is unknown (Error code: sec_error_unknown_issuer)" when visiting a website with a https URL, then this means that Firefox is not able to chain the websites certificate to a trusted Certificate Authority.

This could be a problem with the server, or it could be that somebody is impersonating the server or eavesdropping on your connection. It is generally not a bug with Firefox.

If a site provides a certificate signed by an intermediate CA (one which is not in the root store, but with a trust chain to an existing root CA), the server must provide the intermediate certificates. Failure to do this will result in this error if the intermediate certificates do not already exist in your certificate store.

For certificates signed by RapidSSL (Geotrust)

On December 9, 2010, Geotrust updated their certificate signing process and all certificates issued after this date require the installation of the RapidSSL intermediate on the server. Some sites forget to do this, which results in this error. This is a bug with the website

See http://blog.clickssl.com/2010/12/rapidssl-error-on-firefox-this-connection-is-untrusted/

This online validation tool can tell you which intermediate a server is missing

Requests for inclusion of new CA's

In some cases when experiencing "unknown issuer" errors when visiting certain sites, it may be tempting to open a bug report to request that the issuer CA's certificate is added to the root store shipped with Firefox. There is a well defined process for CA's to request that their certificates are added to the Firefox root store. Adding a certificate to the root store means that the browser places ultimate trust in the certificate owner on our users behalf.

We don't have our own process for verifying applications for inclusion of new certificates, or a process to ensure the continued integrity of the owning authorities once these certificates have been added. We will not bypass the upstream process under any circumstances, so please don't make these types of requests. Doing this without ensuring the integrity of a CA would undermine the entire trust system on the web. Requests of this type will be rejected.

Problems launching external applications

Ubuntu ships an Apparmor profile with Firefox, but this is disabled by default. If you have problems opening files in external applications from Firefox, or problems with extensions which need to start external helpers, then please make sure that the Apparmor profile is disabled or in complain mode before reporting a bug.

To make sure that the profile is not in enforce mode, run sudo aa-status. You will see output which looks a bit like this:

apparmor module is loaded.
18 profiles are loaded.
18 profiles are in enforce mode.
0 profiles are in complain mode.
6 processes have profiles defined.
6 processes are in enforce mode.
   /sbin/dhclient (7094)
   /usr/lib/telepathy/mission-control-5 (2397)
   /usr/lib/telepathy/telepathy-* (4975)
   /usr/lib/telepathy/telepathy-* (7101)
   /usr/lib/telepathy/telepathy-* (7102)
   /usr/sbin/cupsd (1210)
0 processes are in complain mode.
0 processes are unconfined but have a profile defined.

If there are entries starting with "/usr/lib/firefox" in the section "profiles are in enforce mode", then the Firefox profile has been enabled and set to enforce mode. In this case, please set it to complain mode and try again. To do this, please run sudo aa-complain /usr/bin/firefox. (Note, you will need to install apparmor-utils to do this)

If this works and the particular executable is from a software package in the Ubuntu archive, then we may consider adding an exception to the Apparmor profile. In this case, please report a bug using Apport. If the executable is from 3rd party software outside of the Ubuntu archive, then you will need to either keep the Apparmor profile disabled, or add an exception locally in /etc/apparmor.d/local/usr.bin.firefox.

See AppArmor

"The bookmarks and history system will not be functional"

If you see this error when starting Firefox and you are unable to access or modify your bookmarks, please take a look at this support article: The bookmarks and history system will not be functional.

This is not usually a bug, but is normally caused by a corrupt places.sqlite or broken permissions in your profile folder. Please don't report a bug about this, unless you are unable to resolve the issue by following the steps in the support article.

XML errors and broken UI after upgrade

After each release, some of our users report bugs that look a bit like this:

 XML Parsing Error: error in processing external entity reference
 Location: jar:file:///usr/lib/firefox/chrome/toolkit.jar!/content/global/netError.xhtml
 Line Number 10, Column 3:  %netErrorDTD;

Other symptoms include missing UI elements after an upgrade or other kinds of XML errors in dialogue boxes or on firefox's stderr.

This is one of the things that typically happens if you don't restart your Firefox after an upgrade. Please do not report this as a bug. There is already a bug report open about this.

Closed Bug Reports

If you find your bug report to be closed, it has been done by someone on our team for specific reasons. If you have a problem or wish to dispute the action, please use the bug report to ask for more information.

Bug Triage and Procedures

Visit BugProcedures for an Introduction and best practices on how to process Mozilla bugs.

Further reading

CategoryMozillaTeam, CategoryBugSquad, CategoryDebugging

MozillaTeam/Bugs (last edited 2012-11-16 11:57:21 by chrisccoulson)