400 Bad Request
The HTTP 400 Bad Request client error response status code indicates that the server would not process the request due to something the server considered to be a client error. The reason for a 400 response is typically due to malformed request syntax, invalid request message framing, or deceptive request routing.
Clients that receive a 400 response should expect that repeating the request without modification will fail with the same error.
Status
400 Bad Request Examples
Malformed request syntax
Assuming a REST API exists with an endpoint to manage users at http://example.com/users and a POST request with the following body attempts to create a user, but uses invalid JSON with unescaped line breaks:
POST /users HTTP/1.1 Host: example.com Content-Type: application/json Content-Length: 38 { "email": "b@example.com ", "username": "b.smith" } If the content is in a valid format, we would expect a 201 Created response or another success message, but instead the server responds with a 400 and the response body includes a message field with some context so the client can retry the action with a properly-formed request:
HTTP/1.1 400 Bad Request Content-Type: application/json Content-Length: 71 { "error": "Bad request", "message": "Request body could not be read properly.", } Specifications
| Specification |
|---|
| HTTP Semantics # status.400 |