Start a multipart upload and get per-part URLs

For large files. Returns one presigned URL per part; PUT each part and keep its ETag. file_size is required and is used only to plan part_size and num_parts. Rate limit: 120 requests per minute.

Like /api/v1/upload, this creates the job and is not safe to retry blindly.

Authenticate with your key in the X-API-Key header — Authentication.

Request body

Required. application/json

• model string default: zephyr

  The transcription model. One today.

• output_type string default: json

  Format of the stored transcript at download_url.

  One of json, txt, srt, vtt, docx, pdf

• word_timestamps boolean default: true

  Per-word start and end times.

• speaker_labels boolean default: true

  Diarize, labelling turns SPEAKER_1, SPEAKER_2 and so on, dense and numbered from one in order of first appearance.

• nltk boolean default: true

  Punctuation and sentence segmentation.

• custom_vocabulary string[] | null

  Domain terms to bias towards — names, jargon, product names.

• callback_url string (uri) | null

  Webhook to POST on completion or permanent failure. The body is signed with HMAC-SHA256 in X-SR-Signature, and carries X-SR-Event and X-SR-Delivery.

• file_size integer required
• part_size integer | null

  Bytes per part. Clamped to what S3 allows, and raised automatically if the file would otherwise need more than 10,000 parts.

Responses

• 200 Multipart upload started.
• 400 The request was understood but cannot be acted on — for example, completing an upload whose bytes never arrived.
• 401 Missing, malformed or revoked API key.
• 402 The account is out of credit. Top up, or turn on auto-recharge, and retry. Reads and cancellations keep working.
• 413 The file exceeds the limit for this route: 10 GB through the upload routes, 200 MB streaming to /api/v1/transcribe.
• 422 A field is missing or the wrong type. The body names the offending field.
• 429 Too many requests for this endpoint. Back off and retry; the official SDKs do this for you.

200 response fields

• job_id string (uuid) required
• upload_id string required
• download_url string (uri) required
• part_size integer required
• num_parts integer required
• parts object[] required
• expires_in integer required

Related endpoints

• Finish a multipart upload and enqueue the job POST /api/v1/upload/multipart/complete
• Abandon a multipart upload POST /api/v1/upload/multipart/abort