***

title: Word timestamps
description: Return word-level timing metadata from Pulse STT
-------------------------------------------------------------

<Badge color="green">
  Pre-Recorded
</Badge>

<Badge color="purple">
  Real-Time
</Badge>

Word timestamps provide precise timing information for each word in the transcription, enabling you to generate captions, subtitles, and align transcripts with audio playback. Use these offsets to generate captions, subtitle tracks, or to align transcripts with downstream analytics.

## Enabling Word Timestamps

### Pre-Recorded API

Add `word_timestamps=true` to your Pulse STT query parameters. This works for both raw-byte uploads (`Content-Type: audio/wav`) and JSON requests with hosted audio URLs.

#### Sample request

```bash
curl --request POST \
  --url "https://waves-api.smallest.ai/api/v1/pulse/get_text?model=pulse&language=en&word_timestamps=true" \
  --header "Authorization: Bearer $SMALLEST_API_KEY" \
  --header "Content-Type: audio/wav" \
  --data-binary "@/path/to/audio.wav"
```

### Real-Time WebSocket API

Add `word_timestamps=true` to your WebSocket connection query parameters when connecting to the Pulse STT WebSocket API.

```javascript
const url = new URL("wss://waves-api.smallest.ai/api/v1/pulse/get_text");
url.searchParams.append("language", "en");
url.searchParams.append("encoding", "linear16");
url.searchParams.append("sample_rate", "16000");
url.searchParams.append("word_timestamps", "true");

const ws = new WebSocket(url.toString(), {
  headers: {
    Authorization: `Bearer ${API_KEY}`,
  },
});
```

## Output format & field of interest

Responses include a `words` array with `word`, `start`, `end`, and `confidence` fields. When diarization is enabled, the array also includes `speaker` (integer ID for realtime, string label for pre-recorded) and `speaker_confidence` (0.0 to 1.0, realtime only) fields.

### Pre-Recorded API Response

```json
{
  "status": "success",
  "transcription": "Hello world.",
  "words": [
    { "start": 0.0, "end": 0.5, "speaker": "speaker_0", "word": "Hello" },
    { "start": 0.6, "end": 0.9, "speaker": "speaker_0", "word": "world." }
  ],
  "utterances": [
    { "text": "Hello world.", "start": 0.0, "end": 0.9, "speaker": "speaker_0" }
  ]
}
```

The response of Pre-Recorded API includes the utterances field, which includes sentence level timestamps.

### Real-Time WebSocket API Response

```json
{
  "type": "transcription",
  "status": "success",
  "session_id": "00000000-0000-0000-0000-000000000001",
  "transcript": "Hello, how are you?",
  "is_final": true,
  "is_last": false,
  "language": "en",
  "words": [
    {
      "word": "Hello",
      "start": 0.0,
      "end": 0.5,
      "confidence": 0.98
    },
    {
      "word": "how",
      "start": 0.6,
      "end": 0.8,
      "confidence": 0.95
    },
    {
      "word": "are",
      "start": 0.8,
      "end": 1.0,
      "confidence": 0.97
    },
    {
      "word": "you?",
      "start": 1.0,
      "end": 1.3,
      "confidence": 0.99
    }
  ]
}
```

<Note>
  When `diarize=true` is enabled, the `words` array also includes `speaker` (integer ID) and `speaker_confidence` (0.0 to 1.0) fields.
</Note>

## Response Fields

<table>
  <thead>
    <tr>
      <th>
        Field
      </th>

      <th>
        Type
      </th>

      <th>
        When Included
      </th>

      <th>
        Description
      </th>
    </tr>
  </thead>

  <tbody>
    <tr>
      <td>
        `word`
      </td>

      <td>
        string
      </td>

      <td>
        `word_timestamps=true`
      </td>

      <td>
        The transcribed word
      </td>
    </tr>

    <tr>
      <td>
        `start`
      </td>

      <td>
        number
      </td>

      <td>
        `word_timestamps=true`
      </td>

      <td>
        Start time in seconds
      </td>
    </tr>

    <tr>
      <td>
        `end`
      </td>

      <td>
        number
      </td>

      <td>
        `word_timestamps=true`
      </td>

      <td>
        End time in seconds
      </td>
    </tr>

    <tr>
      <td>
        `confidence`
      </td>

      <td>
        number
      </td>

      <td>
        `word_timestamps=true`

         (realtime only)
      </td>

      <td>
        Confidence score for the word (0.0 to 1.0)
      </td>
    </tr>

    <tr>
      <td>
        `speaker`
      </td>

      <td>
        integer (realtime) / string (pre-recorded)
      </td>

      <td>
        `diarize=true`
      </td>

      <td>
        Speaker label. Real-time API uses integer IDs (0, 1, ...), pre-recorded API uses string labels (speaker_0, speaker_1, ...)
      </td>
    </tr>

    <tr>
      <td>
        `speaker_confidence`
      </td>

      <td>
        number
      </td>

      <td>
        `diarize=true`

         (realtime only)
      </td>

      <td>
        Confidence score for the speaker assignment (0.0 to 1.0)
      </td>
    </tr>
  </tbody>
</table>

## Use Cases

* **Caption generation**: Create synchronized captions for video or live streams
* **Subtitle tracks**: Generate SRT or VTT subtitle files
* **Analytics**: Align transcripts with audio playback for detailed analysis
* **Search**: Enable time-based search within audio content