404 Not Found Root Cause Guide

Problem

The final response for a page or route is 404 Not Found.

Symptoms

• HTTP Check shows a final status code of 404.
• The failure only appears after redirects complete.
• Specific assets or route patterns are missing while other pages work.

Top 3 Causes

1. Missing deployment artifact or wrong path - The file, route, or resource does not actually exist.
2. Broken rewrite or redirect logic - Valid requests are being sent to a non-existent final path.
3. Wrong host or environment - The request lands on a different app, environment, or origin than expected.

Diagnose with DechoNet

• HTTP Check to trace the final URL and full redirect path.
• DNS Lookup to make sure the hostname resolves to the correct target service.

Resolution Checklist

• Verify that the final 404 path exists in your deployed output or route definitions.
• Review redirect and rewrite rules for accidental path changes.
• Confirm www, apex, subdomain, and locale-prefixed routes all point to the intended app.
• Check whether deployment base path and trailing slash policies are consistent.
• Re-run HTTP Check and confirm the final route no longer returns 404.

When to Escalate

• Escalate if your deployment pipeline is dropping files or route output unexpectedly.
• Escalate to the application owner if route matching or rewrite logic is centrally controlled.