index.md

---

title: tabs.detectLanguage()
slug: Mozilla/Add-ons/WebExtensions/API/tabs/detectLanguage
page-type: webextension-api-function
tags:
  - API
  - Add-ons
  - Extensions
  - Method
  - Non-standard
  - Reference
  - WebExtensions
  - detectLanguage
  - tabs
browser-compat: webextensions.api.tabs.detectLanguage

---

{{AddonSidebar()}}

Detects the primary language of the content in a tab, using the Compact Language Detector (CLD).

This is an asynchronous function that returns a Promise.

Syntax

let detecting = browser.tabs.detectLanguage(
  tabId,                  // optional integer
  callback                // optional function
)

Parameters

• tabId {{optional_inline}}

  • : integer. Defaults to the active tab of the current window.

• callback {{optional_inline}}

  • : function. Currently, if a tabId is specified, this method uses this callback to return the results instead of returning a promise. The callback receives as its only input parameter a string containing the detected language code such as en or fr.

Return value

A Promise that will be fulfilled with a string representing an ISO language code such as en or fr. For a complete list of languages supported by this method, see kLanguageInfoTable. For an unknown language, "und" will be returned (but see bug 1288263). If any error occurs the promise will be rejected with an error message.

Examples

Detect and log the language of the active tab when the user clicks a browser action:

function onLanguageDetected(lang) {
  console.log(`Language is: ${lang}`);
}

function onError(error) {
  console.log(`Error: ${error}`);
}

browser.browserAction.onClicked.addListener(() => {
  browser.tabs.detectLanguage().then(onLanguageDetected, onError);
});

Detect and log the language of every open tab when the user clicks a browser action (note that this example requires the "tabs" permission):

function onLanguageDetected(url, lang) {
  console.log(`Language in ${url} is: ${lang}`);
}

function onError(error) {
  console.log(`Error: ${error}`);
}

function detectLanguages(tabs) {
  for (const tab of tabs) {
    browser.tabs
      .detectLanguage(tab.id)
      .then((lang) => onLanguageDetected(tab.url, lang), onError);
  }
}

browser.browserAction.onClicked.addListener(() => {
  browser.tabs.query({}).then(detectLanguages, onError);
});

{{WebExtExamples}}

Browser compatibility

{{Compat}}

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