 Thomas Steiner [GitHub](https://github.com/tomayac) [LinkedIn](https://www.linkedin.com/in/thomassteinerlinkedin) [Mastodon](https://toot.cafe/@tomayac) [Bluesky](https://bsky.app/profile/tomayac.com) [Homepage](https://blog.tomayac.com/)
Published: September 24, 2024, Last updated: May 20, 2025
Browser Support
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[Source](https://developer.mozilla.org/docs/Web/API/LanguageDetector)
Before translating text from one language to another, you must first determine
what language is used in the given text. Previously, translation required
uploading the text to a cloud service, performing the translation on the server,
then downloading the results.
The Language Detector API works client-side, which means you can protect user
privacy. While it's possible to ship a specific library which does
this, it would require additional resources to download.
## When to use language detection
The Language Detector API is primarily useful in the following scenarios:
- Determine the language of input text, so it can be translated.
- Determine the language of input text, so the correct model can be loaded for language-specific tasks, such as toxicity detection.
- Determine the language of input text, so it can be labeled correctly, for example, in online social networking sites.
- Determine the language of input text, so an app's interface can be adjusted accordingly. For example, on a Belgian site to only show the interface relevant to users who speak French.
## Get started
The **Language Detector** and **Translator APIs** work in Chrome on desktop.
These APIs don't work on mobile devices.
Run feature detection to see if the browser supports the Language Detector API.
if ('LanguageDetector' in self) {
// The Language Detector API is available.
}
> [!TIP]
> **Tip:** Use the [@types/dom-chromium-ai](https://www.npmjs.com/package/@types/dom-chromium-ai) npm package to get TypeScript typings for the Prompt API and other built-in AI APIs for easier access in your codebase.
### Model download
Language detection depends on a model that is fine-tuned for the specific
task of detecting languages. While the API is built in the browser, the model
is downloaded on-demand the first time a site tries to use the API. In Chrome,
this model is very small by comparison with other models. It might already be
present, as this model is used by other Chrome features.
To determine if the model is ready to use, call the asynchronous
[`LanguageDetector.availability()`](https://developer.chrome.com/docs/ai/get-started#model_download)
function. If the response to `availability()` was `downloadable`, listen for
download progress and inform the user, as the download may take time.
To trigger the download and instantiate the language detector, check for
[user activation](https://developer.chrome.com/docs/ai/get-started#user-activation). Then, call the
asynchronous `LanguageDetector.create()` function.
const detector = await LanguageDetector.create({
monitor(m) {
m.addEventListener('downloadprogress', (e) => {
console.log(`Downloaded ${e.loaded * 100}%`);
});
},
});
### Run the language detector
The Language Detector API uses a ranking model to determine which language is
most likely used in a given piece of text. *Ranking* is a type of machine
learning, where the objective is to order a list of items. In this case, the
Language Detector API ranks languages from highest to lowest probability.
> [!NOTE]
> **Note:** The Language Detector API is trained on a set of languages, which is not wholly inclusive of every language that exists. This means the API cannot detect every language with complete accuracy. From Chrome 132, you can check if a given language is available for detection.
The `detect()` function can return either the first result, the likeliest
answer, or iterate over the ranked candidates with the level of confidence.
This is returned as a list of `{detectedLanguage, confidence}` objects. The
`confidence` level is expressed as a value between `0.0` (lowest confidence)
and `1.0` (highest confidence).
const someUserText = 'Hallo und herzlich willkommen!';
const results = await detector.detect(someUserText);
for (const result of results) {
// Show the full list of potential languages with their likelihood, ranked
// from most likely to least likely. In practice, one would pick the top
// language(s) that cross a high enough threshold.
console.log(result.detectedLanguage, result.confidence);
}
// (Output truncated):
// de 0.9993835687637329
// en 0.00038279531872831285
// nl 0.00010798392031574622
// ...
> [!CAUTION]
> **Caution:** Very short phrases and single words should be avoided, as the accuracy of the results will be low. If you commonly work with shorter text, experiment with your priority languages, review the reported confidence, and return the result as unknown when the confidence is too low.
## API playground
Experiment with the Language Detector API in our
[API playground](https://chrome.dev/web-ai-demos/translation-language-detection-api-playground/). Enter text written in different languages in the textarea.
## Permission Policy, iframes, and Web Workers
By default, the Language Detector API is only available to top-level windows and to their
same-origin iframes. Access to the API can be delegated to cross-origin iframes
using the Permission Policy `allow=""` attribute:
The Language Detector API isn't available in Web Workers. This is due to the
complexity of establishing a responsible document for each worker in order to
check the Permissions Policy status.
## Share your feedback
We want to see what you're building with the Language Detector API. Share your
websites and web applications with us on [X](https://x.com/ChromiumDev),
[YouTube](https://www.youtube.com/user/ChromeDevelopers), and
[LinkedIn](https://www.linkedin.com/showcase/chrome-for-developers/).
If you have feedback on Chrome's implementation, file a
[Chromium bug](https://new.crbug.com/).
[Join the Early Preview Program](https://developer.chrome.com/docs/ai/join-epp)
for an early look at new built-in AI APIs and access to discussion on our
mailing list.