HTTP Status Codes & Response Header Reference
Fast searchable reference for all HTTP status codes (1xx-5xx) and security headers. Includes RFC specifications, REST API patterns, and SEO crawler impact.
Displaying 24 HTTP Status Codes & Headers
🔗 SEO Impact: 301 vs 302 vs 308 Redirects
A 301 Moved Permanently informs Googlebot to transfer all existing PageRank link equity to the destination URL and update search index listings. A 302 Found tells crawlers the move is temporary, preserving the old URL in search indices. A 308 Permanent Redirect behaves like a 301 but strictly prohibits the browser from mutating HTTP POST requests into GET requests.
About this tool
How to use it
- Search for any HTTP status code number (e.g., 404, 502), response name, or HTTP header in the search box.
- Use category filters to isolate 2xx Success, 3xx Redirection, 4xx Client Errors, 5xx Server Errors, or Security Headers.
- Review official RFC standards specifications, REST API usage guidance, and SEO crawler indexing impacts.
- Check actionable fix recommendations to resolve production gateway crashes or authorization timeouts.
Why it matters
HTTP status codes regulate how browsers, APIs, proxies, and search engines communicate over the web. Confusing a temporary 302 redirect with a permanent 301 can devastate SEO rankings, while misunderstanding 401 vs 403 halts API development. A clean developer reference provides instant clarity.
When to use it
Use this reference when debugging backend server errors (Nginx, Gunicorn, Node.js), writing RESTful API endpoints, or auditing SEO site migrations.
Good to know
Compliant with official IETF RFC 9110 (HTTP Semantics), RFC 9111 (HTTP Caching), and W3C Security specifications.
Common questions
What is the difference between a 401 and 403 status code?
401 Unauthorized means the client has not provided valid authentication credentials (e.g. missing or expired API token). 403 Forbidden means the client's identity is verified, but their account lacks permissions to view the resource.
What causes a 502 Bad Gateway error?
A 502 error happens when a reverse proxy server (such as Cloudflare, Nginx, or AWS ALB) attempts to forward a request to an upstream application backend (Node.js, Python, PHP), but the backend process has crashed, timed out, or returned an unreadable response.
How does a 301 redirect affect SEO?
A 301 redirect signals search engines that a page has permanently moved. Google transfers existing PageRank link equity to the new destination URL and replaces the old URL in search listings.
What is HSTS?
Strict-Transport-Security (HSTS) is a security response header that instructs web browsers to only ever connect to a domain using encrypted HTTPS, completely blocking insecure HTTP downgrade attacks.