Send a document/file
POST/api/sessions/:sessionId/messages/send-document
Send a document/file
Request
Responses
- 201
- 400
- 409
- 413
- 501
Document sent
Session not active or invalid request
The session is not connected — an engine exists for it but is not ready: disconnected, reconnecting, or still initializing, so the request never reached WhatsApp. Wait for ready and retry. A session that was never started answers 400 instead, and the session lifecycle routes answer 409 for a conflicting state rather than this. One window answers this while the session still reads ready: WhatsApp Web periodically reloads its own page and the engine re-injects into it — for those few seconds the answer is a 409 naming the reload; retry shortly.
The decoded base64 media exceeds the media byte cap (MEDIA_DOWNLOAD_MAX_BYTES, 50 MiB by default). A whole request is separately bounded by BODY_SIZE_LIMIT (25 mb by default), and base64 inflates by about a third, so a large send usually meets that coarser limit first: the body parser rejects the request before this check runs.
Sending media to a channel (<id>@newsletter) is not supported by the whatsapp-web.js engine — the page method it needs was removed by a WhatsApp Web update. Text to a channel still works.