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HTTP Code: 501 (Not Implemented)

HTTP Status Code Reference

Status Category

5xx — Server Error

Meaning & Definition

The server does not support the functionality required to fulfill the request.

Common Causes

  • Unsupported HTTP methods (e.g. PATCH or TRACE on static server)
  • Unimplemented API route handlers

How to resolve HTTP code errors

1. Inspect Logs: Check server logs (e.g. error.log) to locate runtime exceptions or database disconnects.

2. Test Endpoint: Use our Uptime Checker or redirects prober to verify response headers and payload size.

3. Configure Rules: Implement custom redirect rules or error fallback paths below in Nginx/Apache config.

Nginx Configuration Setup

if ($request_method !~ ^(GET|HEAD|POST)$ ) {
  return 501;
}

Apache Configuration Setup

<LimitExcept GET POST HEAD>
  Require all denied
</LimitExcept>

Standard HTTP Status Codes

HTTP 100HTTP 101HTTP 200HTTP 201HTTP 202HTTP 204HTTP 206HTTP 301HTTP 302HTTP 303HTTP 304HTTP 400HTTP 401HTTP 403HTTP 404HTTP 408HTTP 409HTTP 410HTTP 413HTTP 415HTTP 422HTTP 429HTTP 451HTTP 500HTTP 501HTTP 502HTTP 503HTTP 504

HTTP Diagnostic Tools

Website Uptime Checker — Monitor HTTP response codes in real-timeHTTP Headers Inspector — Examine server response headers and status codesSSL Certificate Checker — Verify HTTPS configuration and redirectsIT Expert AI — Ask about server configuration and HTTP issues

Authoritative Standards

IETF RFC 9110 — HTTP Semantics (June 2022, current standard)MDN Web Docs — HTTP Response Status Codes ReferenceIANA HTTP Status Code Registry

HTTP status codes standardized in RFC 9110. IANA maintains the official registry of all assigned codes.