Saturday, January 17, 2009

How to change locale in Mozilla Firefox

... or How to change language in Mozilla Firefox ...
... or How to change the language of the Firefox menu bar

We might need to switch to a different language in Mozilla Firefox (User Interface, Spell Checker Dictionary, Website content and error messages) to test applications behavior with various internationalized testing conditions (localization or internationalization testing or automatic Globalization Support)


On Windows
We'll download any Windows specific language version from

After installing all consecutive specific versions to the same path (every language must be downloaded and installed), we can manually change the following Mozilla Firefox variables.

Typing about:config on the address var, we can filter and change variables (with the right Windows permissions):


Possible values:
(ISO 639-1 Code)

IE. (en,en-us,sv,sv-se)

Another easy and versatile way is to install Firefox Add-On "Quick Locale Switcher"
It allows you to quickly change and apply a different locale related setting from the tools menu, the statusbar, or your Toolbar.

After selected language and restarted Mozilla Firefox, our browser automatically goes to the right place.

On Linux
We'll download any Linux specific language version from

We can decompress to an specific folder (one per language) and call the right one by some script and install Firefox Add-On "Quick Locale Switcher" from

NOTE: we can also install OPIE from or FEBE to selectively backup and restore extensions if we want to try different configurations.
Or simply do backup (Firefox_Dir\defaults\profile) = file prefs.js

Links, References:

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