HTTP Response Explainer
Paste a raw HTTP response line, header block, or JSON error payload to decode status semantics, validate required RFC headers, and isolate API integration defects.
Paste an HTTP response above or click a preset to inspect status codes, headers, and protocol hints.
How HTTP Response Diagnostics Work
When diagnosing network anomalies and failed API requests, the HTTP response message contains three critical layers of diagnostic evidence:
1. The Status Line
The status line (e.g., HTTP/1.1 401 Unauthorized) establishes the high-level protocol classification:
- 4xx (Client Error): Rejection occurred because the request was malformed, unauthorized, or invalid.
- 5xx (Server Error): The server failed while attempting to fulfill an otherwise valid request.
2. Response Headers
Headers provide protocol-level instructions that dictate client behavior:
WWW-Authenticate:Challenges clients on 401 errors.Allow:Declares valid methods on 405 errors.Retry-After:Coordinates cooldown on 429 / 503 responses.Access-Control-*:Governs browser CORS permissions.
3. Problem Details (RFC 7807)
Modern REST APIs return structured JSON payloads using the application/problem+json media type, providing human-readable details and request correlation IDs.
Frequently Asked Questions
Is my data transmitted to any external server?
No. The HTTPLens Response Explainer operates with a Zero-Log architecture. All parsing, regular expression evaluation, and header analysis execute 100% within your client-side JavaScript engine. No network requests are made.
What format can I paste into the input area?
You can paste full raw HTTP message blocks (status line + headers + body), partial header blocks copied from browser DevTools, cURL verbose output (curl -i), or even standalone HTTP status codes (e.g. 401).
How does the tool identify RFC violations?
The analyzer evaluates mandatory specification rules defined in RFC 9110 and RFC 9111. For instance, if an HTTP 401 response is provided without a WWW-Authenticate header, or a 405 response lacks an Allow header, an alert banner is automatically raised.