Zotero's Unicode support allows you to import, store, and cite items in any language. You can change the language of both the Zotero user interface and the citations and bibliographies created by Zotero. Finally, there is an unofficial multilingual version of Zotero, which supports storage of item metadata in more than one language (transliterations and translations).

By default, the user interface (UI) of Zotero (the labels of menu items, tabs, etc.) is displayed in the same language as Firefox. For example, if you download and install the French version of Firefox, your Zotero UI will automatically appear in French. If translations for a language are not available, Zotero's UI will default to US English.

To change the language of the Zotero UI, you can either use the Quick Locale Switcher Firefox add-on (see below), or follow these instructions:

• Type about:config into the Firefox address bar and press Enter. Dismiss the “This might void your warranty!” warning.
• Type “useragent” in the Filter text box. Now double-click the general.useragent.locale preference (or right-click the preference and select Modify), and enter the desired language tag (e.g. “en-US” for US English). See the chrome manifest for all available codes.
• Type “matchOS” in the Filter text box. If the intl.locale.matchOS preference is set to true, double-click to change it to false. Otherwise, Firefox will use your operating system's language instead of the one you just set.
• Restart Firefox.

Changing the value of general.useragent.locale also affects the Firefox UI, Firefox add-ons, and websites that adapt their content based on the Firefox locale.

The Quick Locale Switcher Firefox add-on makes it easier to change the value of general.useragent.locale. After installation of the add-on (and restarting Firefox), go to the Quick Locale Switcher Options window, and check the “User Interface Language (general.useragent.locale preference)” checkbox. You can now use the popup menu of the Quick Locale Switcher to switch the Firefox locale (although you still have to restart Firefox after changing the locale). If it has no effect, you may need to change the intl.locale.matchOS preference (see above).

In Zotero Standalone, the interface language defaults to matching the operating system's language. To override this and use English instead of the operating system's language, open Preferences→Advanced→Open about:config), and set intl.locale.matchOS to false. Then restart Zotero.

To keep your Zotero UI in one language, but use another language for the citations and bibliographies created by Zotero, simply select the citation language you'd like to use from the appropriate location:

• The “Create Bibliography from Selected Item(s)” dialog
• The word processor integration plugin's document preferences window
• The Quick Copy section in the Export pane of the Zotero preferences

You can report mistakes in Zotero's translations in the Zotero forums. If you would like to make larger contributions (like translating the Zotero client into an as of yet unsupported language), see the developer's instructions for localization.

Juris-M, formerly MLZ, is an unofficial version of Zotero that allows you to store transliterations and translations of names, titles and other fields, and create citations and bibliographies that show this information (e.g. “Soseki, Wagahai ha neko de aru [I am a cat] (1905-06)”).

Juris-M is developed by Frank Bennett, a Zotero user. If you would like to try out Juris-M, see the project webpage.