HTTP 4xx
400 Bad Request
The server could not understand the request, usually because it was malformed.
What causes it
- Invalid syntax, a malformed URL, or a request body the server cannot parse.
How to fix it
Check the request payload, headers, and encoding. On an API, validate the JSON body against the expected schema.
Example response
A typical raw HTTP response a client receives for a 400, with the headers this code is defined around.
HTTP/1.1 400 Bad Request
Content-Type: text/html; charset=utf-8Related codes
401Common
UnauthorizedAuthentication is required and has failed or not been provided.403Common
ForbiddenThe server understood the request but refuses to authorize it. Unlike 401, authenticating will not help.404Common
Not FoundThe server could not find the requested resource. The URL may be wrong or the resource may have been removed.405
Method Not AllowedThe HTTP method is not supported for this resource, for example a POST to a read-only endpoint.408
Request TimeoutThe server timed out waiting for the client to finish the request.410
GoneThe resource was intentionally removed and will not come back. A stronger, permanent signal than 404.Know before your visitors do.
Sentinel checks your site around the clock from multiple regions and alerts you the moment it starts returning a 4xx error, so you can fix it before it costs you.