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

# Send audio

> Send a voice note or audio clip via POST /v1/whatsapp/messages/audio.

Use `POST /v1/whatsapp/messages/audio` for voice notes and audio clips. Point at a publicly reachable `media_url`; WhatsApp fetches it **at send time**, so it must be reachable then and serve the correct `Content-Type`. Needs an **open 24-hour window**.

<Warning>
  WhatsApp audio messages **do not support a caption or filename** — there is no `caption` field on this endpoint.
</Warning>

## Endpoint

```http theme={null}
POST https://karibu.briq.tz/v1/whatsapp/messages/audio
```

**Headers:** `X-API-Key` (required), `Content-Type: application/json`.

## Fields

| Field             | Type   | Required   | Notes                                                                                                                 |
| ----------------- | ------ | ---------- | --------------------------------------------------------------------------------------------------------------------- |
| `media_url`       | string | one source | Public HTTPS URL to the audio file.                                                                                   |
| `file_id`         | string | one source | Uploaded media id (first-party). Use `media_url` for external integrations.                                           |
| `to` + `sender`   | —      | target     | Customer number (E.164) and which of your numbers to send from. `sender` is optional when you have one active number. |
| `conversation_id` | uuid   | alt        | Alternative to `to` + `sender`: an existing thread to reply in.                                                       |

## Constraints

|          |                                                                                                                     |
| -------- | ------------------------------------------------------------------------------------------------------------------- |
| Formats  | AAC (`audio/aac`), AMR (`audio/amr`), MP3 (`audio/mpeg`), M4A (`audio/mp4`), OGG (`audio/ogg`, **OPUS codec only**) |
| Max size | 16 MB                                                                                                               |

WAV and FLAC are not supported. A `131053` error usually means OGG that is not OPUS-encoded, or a file over the limit.

## Example

```bash cURL theme={null}
curl -X POST "https://karibu.briq.tz/v1/whatsapp/messages/audio" \
  -H "X-API-Key: YOUR_API_KEY" -H "Content-Type: application/json" \
  -d '{ "to": "255712345678", "media_url": "https://example.com/voice-note.ogg" }'
```

Returns **202** `{ message_id, status: "pending" }`. Then [track delivery](/guides/whatsapp-track-messages). Build and send a live request from the [Send an audio message](/Karibu-WhatsApp/messages/send-audio) reference page.