1. Mozilla
  2. Add-ons
  3. Browser extensions
  4. JavaScript APIs
  5. i18n
  6. i18n.getSystemUILanguage()

i18n.getSystemUILanguage()

Returns the current UI locale of the operating system. This is different from i18n.getUILanguage, which returns the UI locale of the web browser.

Syntax

js
let systemUILanguage = await browser.i18n.getSystemUILanguage()

Parameters

None.

Return value

A Promise fulfilled with an i18n.LanguageCode.

Browser compatibility

Chrome
Edge
Firefox
Opera
Safari
Firefox for Android
Safari on iOS
getSystemUILanguage
Chrome – No support
Chrome
footnote No support
Edge – No support
Edge
footnote No support
Firefox – No support
Firefox
footnote No support
Opera – No support
Opera
footnote No support
Safari – Full support
Safari 18.4 (Release date: 2025-03-31)
footnote Full support
Firefox for Android – No support
Firefox for Android
footnote No support
Safari on iOS – Full support
Safari on iOS 18.4 (Release date: 2025-03-31)
footnote Full support

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Full support
No support

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