Hi, actually it does : https://support.mozilla.org/en-US/kb/use-firefox-interface-other-languages-language-pack#w_how-to-change-the-language-of-the-user-interface

You may want the dictionary for the language also so it spell checks.

Please let us know if this solved your issue or if need further assistance.

Separate Security Issue, please update your Flash 27.0 r0 Flash Player Version: 30.0.0.113 Current Version https://get.adobe.com/flashplayer/otherversions/ Step 1: Select Operating System Step 2: Select A Version (Firefox, . . . .) Note: Other software is offered in the download. <Windows Only>

You need to modify/create a string pref on the about:config page like written in the knowledge base article

• intl.locale.requested = "ja"
  (without the quotes)

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

• http://kb.mozillazine.org/about:config

• https://support.mozilla.org/en-US/kb/use-firefox-interface-other-languages-language-pack

Type intl.locale.requested in the Search field. Double-click the intl.locale.requested preference, if found, or add it as a new preference (see Configuration Editor for Firefox for details). Enter the code of the language you want to use as the string value or leave it blank to use the language of your system.

Doesn't this setting refers to where one resides so that the browser brings up the local contents? I don't reside there. I just want to use the language.

Pkshadow said

You may want the dictionary for the language also so it spell checks.

Does it help with the Japanese language?

Pkshadow said

Separate Security Issue, please update your Flash 27.0 r0

Is the Flash update global or is it browser specific? I've just updated the Flash the other day.

I've read https://developer.mozilla.org/en-US/docs/Mozilla/Command_Line_Options for the sake of being able to switch between two languages.

However it seems to be beyond my depth. I wish there was a much simpler way.

Never mind I might have to leave it at that for the time being.

You can create copies of the Firefox desktop shortcut and add the parameter set set the language to each of them.

Firefox en-US version:

• (64-bit Firefox)
  "C:\Program Files\Mozilla Firefox\firefox.exe" -UILocale en-US

Firefox 'ja' version:

• (64-bit Firefox)
  "C:\Program Files\Mozilla Firefox\firefox.exe" -UILocale ja

Thanks, I've tried both commands. Both open the Firefox.

However they don't bring up version of different language. They just follow the language setting of the intl.locale.

Thanks for your effort and help.

It appears that support for -UILocale has been removed (#1347306) and this switch is no longer mentioned in the command line article on MDN. There is a UI planned for switching the language (#1425941) via about:preferences, but there needs a lot to be done before it is ready, so the only way to switch the language is by modifying intl.locale.requested on the about:config page. You need to close and restart Firefox to make the change effective.

Thanks for all yours help.

You're welcome.