All HTTP Status Codes
400

Bad Request

4xx Client Error

What It Means

The server cannot process the request due to malformed syntax or invalid parameters.

When You'll See It

Returned when request body validation fails, missing required fields, or malformed JSON.

Related Status Codes

422 Unprocessable Entity 415 Unsupported Media Type 413 Payload Too Large

Frequently Asked Questions

What does HTTP 400 mean?

HTTP 400 Bad Request means: The server cannot process the request due to malformed syntax or invalid parameters.

When does a server return 400?

Returned when request body validation fails, missing required fields, or malformed JSON.

Is 400 a client error or server error?

HTTP 400 is a Client Error (4xx) response. This means the issue is on the client side — the request was incorrect or unauthorized.

Looking for all status codes in one place? Use the interactive HTTP Status Codes reference tool to search and browse all codes.