4xx Client Errors
400-499
The server cannot or will not process the request due to something that is perceived to be a client error.
Generic client error response for malformed requests.
The client must authenticate itself to get the requested response.
Returned when authentication is required but has failed or not been provided.
The client does not have access rights to the content.
Returned when user is authenticated but doesn't have permission to access the resource.
The server cannot find the requested resource.
Most common error when a resource doesn't exist at the requested URI.
The request method is known by the server but is not supported by the target resource.
Returned when trying to use POST on a read-only resource, for example.
The request conflicts with the current state of the server.
Commonly returned when trying to create a resource that already exists.
The resource requested is no longer available and will not be available again.
Used when a resource has been permanently deleted.
The request was well-formed but was unable to be followed due to semantic errors.
Commonly returned by APIs when validation fails.
The user has sent too many requests in a given amount of time.
Used for rate limiting to prevent abuse.