post-only mode: only post-only orders and cancels are allowed
The exchange is in post-only mode. You can cancel orders and place orders with `postOnly: true`; non-post-only orders are rejected. The response includes `code: "post_only_mode"` and `retry_after_seconds`, and the same retry delay is also sent in the `Retry-After` HTTP header.
Only post-only orders and cancels are accepted. The response includes retry_after_seconds and a Retry-After header saying when to try again.
Retry? Wait for the exchange
The exchange is in a restricted mode. The same order will keep failing until the mode lifts; there is nothing to fix on your side.
Returned by
- POST /order 5,000 req / 10s
Handling it in code
The CLOB API returns errors as {"error": "..."}. It also rewrites status codes by message, so branch on the text: anything containing "not found" becomes 404 and anything containing "unauthorized" becomes 401.
r = session.post(url, json=payload, headers=headers)
if r.status_code >= 400:
msg = r.json().get("error", "")
if "post-only mode: only post-only orders and cancels are allowe" in msg:
pause_trading()Related errors
- 400Invalid order payload
- 400the order owner has to be the owner of the API KEY
- 400the order signer address has to be the address of the API KEY
- 400'{address}' address banned
- 400'{address}' address in closed only mode
- 503Trading is currently cancel-only. New orders are not accepted, but cancels are allowed.
For errors Polymarket doesn't document, like "order manager not ready" or 403s from the edge, see the full error guide.
Message and status from Polymarket's error reference, synced 2026-10-04.