Invalidrequests

Invalidrequests is a term used to describe client-submitted requests that fail to conform to the rules of a protocol, API contract, or service expectations, resulting in error responses from the server. They arise from issues such as malformed syntax, invalid or missing headers, unsupported HTTP methods, missing required parameters, incorrect data formats, oversized payloads, or requests to non-existent endpoints. Causes include user error, outdated client software, interoperability gaps between components, or deliberate probing by attackers.

In HTTP-based services, servers commonly respond to invalidrequests with specific status codes. Typical responses include 400 Bad Request for syntactic or semantic errors, 411 Length Required when a required Content-Length header is missing, 413 Payload Too Large for oversized bodies, 415 Unsupported Media Type for inappropriate content formats, and 422 Unprocessable Entity for semantic validation failures. Proxies and gateways may also generate or transform invalid requests, sometimes obscuring the original client error.

Handling invalidrequests involves both prevention and clear remediation. Best practices include validating input at the edge and within the application, returning clear, standards-compliant error responses that include machine-readable fields (such as an error code, a human-readable message, and a pointer to the invalid field). Avoid leaking internal server details in error messages. Logging should capture sufficient information for debugging while protecting sensitive data. Consistent error codes and messages, coupled with input validation and strong documentation of API contracts, help clients diagnose and correct issues. Additional defenses such as rate limiting and automated validation can reduce the impact of malformed or abusive requests.

See also: HTTP status codes, input validation, API design, error handling, security considerations.