Functions to internationalize your add-on. You can use these APIs to get localized strings from locale files packaged with your add-on, find out the browser's current language, and find out the value of its Accept-Language header.

For more details on i18n in WebExtensions, see:


A language tag such as "en-US" or "fr".


Gets the accept-languages of the browser. This is different from the locale used by the browser. To get the locale, use i18n.getUILanguage.
Gets the localized string for the specified message.
Gets the UI language of the browser. This is different from i18n.getAcceptLanguages which returns the preferred user languages.
Detects the language of the provided text using the Compact Language Detector.

Browser compatibility

Chrome Edge Firefox Firefox for Android Opera
LanguageCode Yes Yes 45.0 48.0 33
detectLanguage Yes No 47.0 48.0 33
getAcceptLanguages Yes Yes 47.0 48.0 33
getMessage Yes Yes 45.0 48.0 33
getUILanguage Yes Yes 47.0 48.0 No

Edge incompatibilities

Promises are not supported in Edge. Use callbacks instead.

Chrome incompatibilities


Example add-ons


This API is based on Chromium's chrome.i18n API. This documentation is derived from i18n.json in the Chromium code.

Microsoft Edge compatibility data is supplied by Microsoft Corporation and is included here under the Creative Commons Attribution 3.0 United States License.

Document Tags and Contributors

 Contributors to this page: abbycar, wbamberg, chrisdavidmills
 Last updated by: abbycar,