Free & Private Online Browser Utility
HTTP Status Codes Reference & Diagnostics
Search, filter, and inspect HTTP response status codes directly in your browser. Browse complete IETF RFC 9110 specifications across 1xx (Informational), 2xx (Success), 3xx (Redirection), 4xx (Client Errors), and 5xx (Server Errors). Each status code card explains semantic protocol meanings, caching behavior, common developer root causes, and client remediation strategies with zero external telemetry.
How to use
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Step 1: Search or Filter Codes
Type a status number (e.g., 404, 502) or filter by category class (1xx through 5xx).
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Step 2: Review Specification Details
Inspect RFC descriptions, cacheability flags, and whether the response permits a payload body.
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Step 3: Read Remediation Advice
Examine common debugging steps for backend server errors and frontend API integration issues.
Worked example
Input: HTTP Status Code: 429
Output: 429 Too Many Requests | Class: 4xx Client Error | Cacheable: No | RFC: RFC 6585
Based on official IANA HTTP Status Code Registry and RFC specifications.
Tips & limits
- 4xx codes indicate client-side request problems (bad auth, invalid JSON, rate limits); 5xx codes indicate backend server failure.
- A 301 redirect is permanently cached by browsers; use a 302 or 307 temporary redirect during development to prevent aggressive browser caching.
- The 429 status code is conventionally accompanied by a Retry-After header indicating rate limit backoff seconds.
Common problems
- Difference between 401 Unauthorized and 403 Forbidden
401 means the client has not authenticated; 403 means the identity is known but lacks required permissions for the resource.
- Browser reports CORS error alongside HTTP 500
When a backend crashes with a 500 error, it often fails to send Access-Control-Allow-Origin headers, producing a secondary CORS alert.
Frequently Asked Questions (FAQ)
What is the difference between 502 Bad Gateway and 504 Gateway Timeout?
A 502 means an edge proxy received an invalid or closed connection from the upstream server; a 504 means the upstream server failed to respond before the proxy timeout expired.
Are custom non-standard HTTP status codes included?
The reference covers official IETF/IANA standard codes along with widely adopted vendor codes (such as Cloudflare 520–524).
Does browsing status codes make requests to external APIs?
No. The status code reference database is embedded client-side; searching works completely offline.