4xx Client error

400 Bad Request

The server can’t process the request because it is malformed.

A generic client error: invalid JSON, missing required parameters, wrong types or an invalid header.

Common causes and fixes

• Check that the body is valid JSON and that Content-Type matches it.
• Look for missing or misspelled required fields and wrong value types.
• URL-encode query parameters that contain special characters.
• Oversized or malformed cookies can also cause a 400 — try clearing them.

Example response

HTTP/1.1 400 Bad Request
Date: Thu, 22 Oct 2026 08:00:00 GMT

Check a URL’s status with curl -I https://example.com, which prints the status line and headers.

Related status codes

• 422 Unprocessable Content
• 415 Unsupported Media Type
• 413 Content Too Large

Related tools

curl to Code · LLM API Playground · LLM Stream Parser