Preview a group from its invite code, without joining
GET/api/sessions/:sessionId/groups/join-info
Read-only: nothing about the account changes, which is what makes it safe to call on a code from an untrusted source. Supported on both engines.
There is no participant LIST — the account is not a member — only a count, and only when WhatsApp discloses one. Fields the engine does not report are omitted rather than defaulted, because whatsapp-web.js returns an untyped object with no guaranteed shape.
Request
Responses
- 200
- 400
- 404
- 409
- 503
What the invite discloses about the group
Session not started, or no code supplied
No such invite — invalid, expired or revoked
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.
WhatsApp did not answer within the request budget. Deliberately not folded into the 404 above — a query that never came back is not the same claim as a group that does not exist.