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

# Eleven Forced Alignment

> Align a known transcript to audio and get the start and end time of each word. $0.3312 per hour of audio.

`eleven-forced-alignment` aligns a transcript you already have to its audio and returns the start and end time of every word.

| Property | Value |
| - | - |
| Model ID | `eleven-forced-alignment` |
| Endpoint | `POST /v1/audio/alignment` (multipart file or JSON `audio_url`) |
| Output | JSON: `words[]` with `start`, `end`, and `loss`, plus an overall `loss` |
| Limits | Input up to 3,600 seconds, up to 50 MB |
| Billed on | Input length measured by SnapGen, in whole seconds |
| Price | \$0.000092 per second (\$0.00552 per minute, \$0.3312 per hour) |

Confirm live rates on the [SnapGen models page](https://snapgen.org/models). Failed requests are not charged.

<ParamField body="model" type="string" required>
  Set to `eleven-forced-alignment`.
</ParamField>

<ParamField body="file" type="file">
  The audio file, sent as `multipart/form-data`, up to 50 MB. Send `file` or `audio_url`, not both.
</ParamField>

<ParamField body="audio_url" type="string">
  Public `http` or `https` URL of the audio. The gateway downloads it (up to 50 MB). Send `audio_url` or `file`, not both.
</ParamField>

<ParamField body="text" type="string" required>
  The transcript to align, up to 100,000 characters.
</ParamField>

## Request

Upload a local file as `multipart/form-data`:

```bash theme={null}
curl https://api.snapgen.org/v1/audio/alignment \
  -H "Authorization: Bearer $SNAPGEN_API_KEY" \
  -F model=eleven-forced-alignment \
  -F file=@narration.mp3 \
  -F text="The quick brown fox jumps over the lazy dog."
```

Or send JSON with a public `audio_url`:

```bash theme={null}
curl https://api.snapgen.org/v1/audio/alignment \
  -H "Authorization: Bearer $SNAPGEN_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "eleven-forced-alignment",
    "audio_url": "https://example.com/narration.mp3",
    "text": "The quick brown fox jumps over the lazy dog."
  }'
```

The response is JSON with `words[]`, each with `text`, `start`, `end`, and `loss`, plus an overall `loss`.

## Price examples

| Length | Price |
| - | - |
| 1 minute | \$0.00552 |
| 10 minutes | \$0.0552 |
| 1 hour | \$0.3312 |

<Note>
  Synchronous audio endpoints reject `Idempotency-Key`. If a request times out, check your Console request logs before you retry.
  See [Forced alignment](/api-reference/audio-alignment) for every field, the response, and errors.
</Note>