400 Bad Request
The server cannot process the request as sent.
What it means
Malformed syntax, invalid JSON, or a value that fails validation. A good API explains which field is wrong.
What your client should do
Read the error body, fix the request, then send it again. Retrying unchanged will fail again.
Should you retry?
Only after you change the request.
Try it
The free practice API returns this status on demand, with the headers a well-behaved API would send. Call GET /api/play/status/400 from Endpoint Client and open the Explain tab.
Related codes
422 Unprocessable Content
The body is well-formed but semantically invalid.
415 Unsupported Media Type
The server does not accept this body format.
Defined in RFC 9110. All status codes and headers