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4xx Client & Proxy Request

HTTP 404 Not Found — Reverse Proxy & Gateway Troubleshooting

HTTP 404 Not Found means the origin server or CDN edge found no representation matching the requested URI path, or intentionally masks a restricted endpoint behind a 404 response.

Status Code404 Not Found
Specification / OriginRFC 9110 §15.5.5
Failure LayerIngress Router / Origin Static Root
Retry SafetyDo not blind-retry without fixing request syntax, auth, or origin certificate

Interactive HTTP 404 Live Probe & Log Command Builder

Enter your target endpoint below to generate copy-ready curl latency breakdown probes and origin bypass tests:


  

    Related diagnostics:
    Nginx & Caddy Proxy Generator → ·
    X.509 SSL Certificate Decoder → ·
    Offline JWT Expiry Inspector →
  






  
Production Root Causes & Remediation Guide

  
In modern single-page applications (React, Vue, Vite) and Nginx reverse proxies, 404s frequently break deep links when try_files lacks an /index.html fallback, or when a trailing slash in proxy_pass unintentionally strips path prefixes.

  
Step-by-Step Engineering Fix

  
Verify root vs alias directives in Nginx location blocks, add try_files $uri $uri/ /index.html for client-routed SPAs, and audit trailing slashes on proxy_pass upstream definitions.

  
Recommended Nginx / Reverse-Proxy Configuration Snippet

  
location / {
    try_files $uri $uri/ /index.html;
}







  
Frequently Asked Questions (HTTP 404)

  
  

    How does a trailing slash on Nginx proxy_pass cause unexpected 404 errors?
    
Writing proxy_pass http://backend/; strips the matched location prefix before forwarding upstream, whereas proxy_pass http://backend; preserves the full original URI path.

  

  
  

    Which infrastructure layer generates HTTP 404 Not Found?
    
HTTP 404 (RFC 9110 §15.5.5) typically originates at the Ingress Router / Origin Static Root layer. HTTP 404 Not Found means the origin server or CDN edge found no representation matching the requested URI path, or intentionally masks a restricted endpoint behind a 404 response.

  

  
  

    Should API clients automatically retry HTTP 404 responses?
    
Do not blind-retry HTTP 404 without fixing the underlying request payload, authentication token, or origin TLS certificate first.

  

  






  
Browse All 25 Gateway, Proxy & Cloud HTTP Error Guides

  

    
      HTTP 400 (Bad Request)
    
      HTTP 401 (Unauthorized)
    
      HTTP 403 (Forbidden)
    
      HTTP 404 (Not Found)
    
      HTTP 405 (Method Not Allowed)
    
      HTTP 408 (Request Timeout)
    
      HTTP 413 (Content Too Large)
    
      HTTP 422 (Unprocessable Content)
    
      HTTP 429 (Too Many Requests)
    
      HTTP 431 (Request Header Fields Too Large)
    
      HTTP 499 (Client Closed Request)
    
      HTTP 500 (Internal Server Error)
    
      HTTP 501 (Not Implemented)
    
      HTTP 502 (Bad Gateway)
    
      HTTP 503 (Service Unavailable)
    
      HTTP 504 (Gateway Timeout)
    
      HTTP 507 (Insufficient Storage)
    
      HTTP 511 (Network Authentication Required)
    
      HTTP 520 (Web Server Returned an Unknown Error)
    
      HTTP 521 (Web Server Is Down)
    
      HTTP 522 (Connection Timed Out)
    
      HTTP 523 (Origin Is Unreachable)
    
      HTTP 524 (A Timeout Occurred)
    
      HTTP 525 (SSL Handshake Failed)
    
      HTTP 526 (Invalid SSL Certificate)
    
  






  


  
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