> ## Documentation Index
> Fetch the complete documentation index at: https://docs.mentraglass.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Translation

> Real-time translation of speech from the glasses microphone.

`session.translation` turns spoken speech into translated text. Register a handler
for the language pair you care about and results start arriving; the SDK handles
the subscription for you.

```typescript theme={null}
session.translation.to("es", (data) => {
  if (data.isFinal) {
    session.display.render([{type: "text", id: "msg", box: {x: 0, y: 0, w: 576, h: 288}, text: data.text}]);
  }
});
```

Translation needs the `MICROPHONE` permission in your
[manifest](/app-devs/core-concepts/miniapp-manifest). Without it the phone drops
the subscription and no events arrive. The rejection is silent: there is no error
event, your handler just never fires.

## Results

Each event is a `TranslationData`:

| Field            | Type      | Notes                                                                                 |
| ---------------- | --------- | ------------------------------------------------------------------------------------- |
| `text`           | `string`  | The translated text so far.                                                           |
| `isFinal`        | `boolean` | `false` for interim results that keep updating, `true` once the utterance is settled. |
| `sourceLanguage` | `string`  | Language the speech was recognized in.                                                |
| `targetLanguage` | `string`  | Language `text` was translated into.                                                  |
| `originalText`   | `string?` | Source-language text of the same utterance, when the provider supplies it.            |
| `utteranceId`    | `string?` | Stable id correlating interim and final results of one utterance.                     |
| `speakerId`      | `string?` | Speaker id when the provider reports diarization.                                     |

Interim results stream as the user speaks and get replaced; wait for `isFinal` if
you only want settled text. Use `utteranceId` to match an interim result to the
final one that supersedes it.

## Choosing what to listen for

Three methods select which translations reach your handler. They differ only in how
they pin the source and target language.

| Method                            | Listens for                                                                                                |
| --------------------------------- | ---------------------------------------------------------------------------------------------------------- |
| `on(handler)`                     | Every translation event, any source, any target.                                                           |
| `to(target, handler)`             | Any source, translated to `target`. Pass an array of targets to fan one handler across several.            |
| `fromTo(source, target, handler)` | A specific `source` to `target` pair. Pass an array for `target` to fan one source across several targets. |

Each returns an unsubscribe function. `source` and `target` are language tags
(for example `"en"`, `"es"`).

```typescript theme={null}
// Any language the user hears, translated to Spanish.
session.translation.to("es", handler);

// Several targets at once, one handler.
session.translation.to(["es", "fr"], handler);

// A specific direction: English speech to Spanish text.
session.translation.fromTo("en", "es", handler);

// One source fanned across multiple targets.
session.translation.fromTo("en", ["es", "fr"], handler);
```

`on()` is the broad case. It registers cheaply on your side but asks the cloud to
fan every active pair out to you, so reach for `to` or `fromTo` once you know the
language(s) you want.

When the provider supplies `originalText`, you can show the source and the
translation together:

```typescript theme={null}
session.translation.to("es", (data) => {
  if (data.originalText) {
    session.display.showDoubleTextWall(data.originalText, data.text);
  } else {
    session.display.render([{type: "text", id: "msg", box: {x: 0, y: 0, w: 576, h: 288}, text: data.text}]);
  }
});
```

<Note>
  `forLanguagePair(fromLang, toLang, handler)` is a deprecated alias for
  `fromTo(source, target, handler)`. Use `fromTo` in new code; the alias will be
  removed in a future release.
</Note>

## Cleaning up

Every subscription returns an unsubscribe function. `stop()` tears down every
subscription this module owns at once:

```typescript theme={null}
const off = session.translation.to("es", handler);
off();                      // drop this one

session.translation.stop(); // drop all of them
```

`session.translation.hasPermission` tells you whether `MICROPHONE` is declared in
your manifest. It does not tell you whether the user granted the OS prompt: if they
denied it, your handler simply never fires. See
[Permissions](/app-devs/core-concepts/permissions).

<Note>
  Translation gives you translated text. For the untranslated transcript in the
  spoken language, use
  [`session.transcription`](/app-devs/core-concepts/microphone/speech-to-text).
  Subscribing to one does not subscribe you to the other.
</Note>