400
4xx Client ErrorBad Request
The server can't process the request due to a client error like malformed syntax.
400 Bad Request is a catch-all for 'the request itself is broken'. The server couldn't or wouldn't process it because something on the client side is malformed: invalid JSON, a missing required field, a bad query parameter, or a header the server can't parse. The fix is almost always in the request, not the server.
About 4xx Client Error
The request has a problem the client needs to fix, like a bad URL, missing auth, or invalid input.
How to fix 400 Bad Request
- Validate the request body - malformed JSON is the most common cause.
- Check required fields and parameter types against the API docs.
- Inspect headers like Content-Type for typos or wrong values.
- Look at the response body - many APIs explain exactly what failed.