404 Not Found

What causes it

• The URL is wrong — a typo, a stale link, or a case-sensitivity mismatch on a Linux server.
• The route exists in your code but not in the deployed build.
• A rewrite rule is missing, so a single-page app route is being handed to the file server.
• The resource was deleted (410 would be more informative).

How to fix it

• Check the server access log: a 404 with the exact requested path tells you whether the request even reached your application.
• For SPAs, add a catch-all rewrite to `index.html`.
• Serve a useful 404 page with search and links — it is often the highest-traffic error page on a site.
• Do not return 404 with a 200 status ("soft 404"); search engines treat that as a duplicate-content problem.

Other 4xx client error codes

• 400 Bad Request
• 401 Unauthorized
• 402 Payment Required
• 403 Forbidden
• 405 Method Not Allowed
• 406 Not Acceptable
• 407 Proxy Authentication Required
• 408 Request Timeout
• 409 Conflict
• 410 Gone
• 411 Length Required
• 412 Precondition Failed
• 413 Content Too Large
• 414 URI Too Long
• 415 Unsupported Media Type
• 416 Range Not Satisfiable
• 417 Expectation Failed
• 418 I'm a teapot
• 421 Misdirected Request
• 422 Unprocessable Content
• 423 Locked
• 424 Failed Dependency
• 425 Too Early
• 426 Upgrade Required
• 428 Precondition Required
• 429 Too Many Requests
• 431 Request Header Fields Too Large
• 451 Unavailable For Legal Reasons
• 499 Client Closed Request

Back to the full HTTP status code reference