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Send an audio clip and the recipient sees the native iMessage audio message balloon — waveform, play button, scrubber — not a generic file pill.

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Send an audio message

Two-step flow: upload the audio file via POST /v1/files, then send it by file ID. Common formats are accepted — m4a, mp3, wav, caf, aiff. 
import { readFileSync } from "node:fs";
import { createClient } from "@messages-dev/sdk";

const client = createClient();

// 1. Upload the audio file
const file = await client.uploadFile({
  file: readFileSync("clip.m4a"),
  mimeType: "audio/mp4",
  filename: "clip.m4a",
});

// 2. Send it as an audio message
await client.sendAudioMessage({
  from: "+15551234567",
  to: "+15559876543",
  audioMessage: file.id,
});
File IDs are reusable — upload a clip once and send it to many recipients without re-uploading.

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Parameters

FieldRequiredDescription
fromYesSender line handle.
toYesRecipient phone number, Apple ID, or chat ID (cht_...).
audioMessageYesFile ID (file_...) of an audio file uploaded via POST /v1/files.
replyToNoMessage ID or GUID to reply to.

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Requirements

iMessage only — audio messages are not supported on SMS lines. Some lines don’t support audio messages; sending from one of those returns 400 advanced_features_required.

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Supported formats

Common audio formats are accepted:
  • m4a / aac
  • mp3
  • wav
  • caf
  • aiff
The audio is transcoded server-side, so you don’t need to pre-encode.

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Receive an audio message

Inbound voice memos are delivered through the standard message.received webhook. The message payload sets is_audio_message: true and the audio attachment includes a transcription field with the text that iMessage auto-generates on-device: 
{
  "event": "message.received",
  "data": {
    "id": "msg_abc123",
    "chat_id": "cht_def456",
    "sender": "+15559876543",
    "text": null,
    "is_from_me": false,
    "is_audio_message": true,
    "attachments": [
      {
        "filename": "Audio Message.caf",
        "mime_type": "audio/x-caf",
        "size": 24576,
        "url": "https://files.messages.dev/...",
        "transcription": "Hey, can you grab milk on the way home?"
      }
    ],
    "sent_at": 1710000000000
  },
  "timestamp": 1710000000123
}
Download the audio bytes from attachments[0].url and use transcription to read what was said without running speech-to-text yourself.
transcription is generated by Apple on the receiving Mac and may be null on the first delivery if it hasn’t finished yet (usually within a couple of seconds). Non-voice-memo audio attachments (e.g. a drag-and-dropped MP3) arrive with is_audio_message: false and no transcription.
import { verifyWebhook } from "@messages-dev/sdk";

app.post("/webhooks", async (req, res) => {
  const event = await verifyWebhook(
    req.body,
    req.headers["x-webhook-signature"],
    process.env.WEBHOOK_SECRET!,
  );

  if (event.event === "message.received" && event.data.isAudioMessage) {
    const voice = event.data.attachments?.[0];
    console.log(`${event.data.sender} said: ${voice?.transcription ?? "(no transcript yet)"}`);
  }

  res.sendStatus(200);
});