The following document was written to create a central location for tips and tricks that MozQA uses quite often. It is our belief that these will make your life easier when you are testing.

Crash Firefox on Demand

At times, it is actually useful to crash Firefox: for instance, when testing Session Store or testing the crash reporter.

There is an extension that allows you to crash Firefox which can be downloaded from here. Simply download the file and drag it into Firefox. This will allow you install the crashme extension. To cause a crash using this extension, simply select Crash Me Now from the Tools menu and select the type of crash you wish to trigger.

If Firefox is hung, you can crash it by other means.

Forcing Extension Compatibility

** Warning: You should use this for testing purposes only. Using incompatible add-ons has the potential to create serious problems in Firefox ** You can also force compatibility of an add-on. Essentially this prevents Firefox from blocking installation of incompatible add-ons. Simply do the following:

1. Type about:config in the location bar and press enter.

2. You'll be warned about editing preferences but you can bypass this warning by selecting I'll be careful, I promise!

3. Right click anywhere in the list of preferences and create a new Boolean preference called extensions.checkCompatibility. Give this preference a value of false.

When you install an add-on after adding this preference, you will still be warned about installing incompatible add-ons but Firefox will allow you to install the add-on.

Email SSL Certificates

You may find that you need to get a secure email SSL certificate. Should this need arise, you can get one by going to and selecting Products > Free Personal Email Certificates.

Printing Images

Certain images will not print by default. For example, the image at the top of does not normally print. To enable printing of these images, check Print Background Colors and Print Background Images under the Appearance section of the Print dialog.

Installing Older Versions of Flash

There may be times when you want to install an older version of Flash, perhaps for testing or personal use. You can find installers for older versions of flash here.

Simulating Slow(er) Internet Connections

Sometimes being fast is problematic, especially when you're trying to confirm bugs that happen for dial-up/satellite users, or over a saturated network. See this Macworld article for tips on Mac OS X. (In case that resource goes down/missing, here's how to do it.) Example:

sudo ipfw pipe 1 config bw 15KByte/s

creates a pipe that only allows up to 15KB/s to go through. Then:

sudo ipfw add 1 pipe 1 src-port 80

will attach that pipe to the outgoing traffic on port 80, effectively limiting the outgoing traffic of the web server.

sudo ipfw delete 1

will remove the pipe from the port.


Set up multiple profiles in Firefox



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