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HTTP Status Codes

HTTP 400 Bad Request

400 Bad Request

The server rejected the request because it considers the request malformed or invalid and will not process it as sent.

400 Bad Requestgeneral

Observed message

400 Bad Request

Why it happens

  • The request syntax, framing, or payload is malformed.
  • Headers, cookies, or query parameters contain invalid values.
  • The server considers the request routing or formatting invalid.

How to fix it

  1. Review the request URL, headers, and body for malformed input.
  2. Validate any JSON, form data, or query parameters being sent.
  3. Retry only after correcting the request format rather than sending the same request unchanged.

Official reference

MDN: 400 Bad Request

Related errors

404 Not FoundHTTP 404 Not Found410 GoneHTTP 410 Gone401 UnauthorizedHTTP 401 Unauthorized403 ForbiddenHTTP 403 Forbidden

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400 Bad Request: what it means and how to fix it | Error Atlas