HTTP 404 Not Found

Plain-English meaning

The server is reachable, but the URL does not map to a resource.

Why it happens

The path changed, was deleted, or never existed at that location.

Common causes

• Deploy changed routes without redirect rules
• Case-sensitive paths differ between environments
• Rewrite rules strip required URL segments
• Static files were not published to the target environment

What to check first

Confirm exact URL from logs, verify route registration, and check rewrite order in web server config.

How to fix it

Restore missing route/content, add 301 mappings for moved URLs, and enforce broken-link checks in CI.

Example signal

GET /docs/old-api
HTTP/1.1 404 Not Found

Related links

404 · 429 · 500 · 502 · 503 · 504 · Cloudflare 522 · Nginx 499 · ERR_CONNECTION_REFUSED

Client errors hub · Server errors hub · Comparison pages · Homepage