400
Client Error
400 Bad Request
The server cannot process the request due to malformed syntax.
Definition (RFC 9110)
HTTP status code 400 400 Bad Request is defined in RFC 9110 (HTTP Semantics), Section 15.5.1 — the current authoritative specification for HTTP semantics, published June 2022, which obsoletes the older RFC 7231 and RFC 2616.
Description
The 400 Bad Request status code indicates that the server cannot or will not process the request due to something perceived as a client error. This could be malformed request syntax, invalid request message framing, or deceptive request routing.
Common Causes
- Malformed JSON or XML in request body
- Invalid URL encoding
- Missing required parameters
- Request body too large
- Invalid header values
How to Fix
- Check request body format and encoding
- Validate all required parameters are present
- Ensure Content-Type header matches body format
- Check URL encoding of special characters
- Reduce request size if too large
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