HTTP status codes

Server received headers and is ready to accept the request body. Used when uploading large files.

Protocol switch requested by the client. Typical use case — establishing a WebSocket connection.

Preliminary headers sent before the main response. Lets the browser start loading resources earlier — improves LCP.

Page exists and is accessible. Search engines index it. The ideal status for all working pages.

Resource successfully created in response to a POST request. Used in APIs, not seen in browsers.

Request succeeded but response has no body. A page with this status will not be indexed.

Partial resource delivery (Range requests). Used for video, audio, and file downloads. Reduces latency and improves Core Web Vitals.

Page has moved permanently. Passes PageRank to the new URL. The primary SEO redirect tool.

Temporary redirect. Does not pass PageRank by default, but may be interpreted as permanent (301) by search engines if used long-term.

Redirects to a result page via GET after a POST request. Used in forms to prevent duplicate submissions.

Resource has not changed since last request — browser uses cached copy. Reduces latency and improves Core Web Vitals on repeat visits.

Temporary redirect that preserves the request method (POST stays POST). Like 302, but stricter — method is not changed.

Permanent redirect that preserves the request method. Like 301, but POST does not become GET. Used in APIs and REST services.

Server could not understand the request due to a syntax error. Occurs with invalid form parameters or malformed data.

Access requires authentication. Search engines cannot access the page — it will not be indexed.

Access forbidden. Pages already indexed may persist temporarily, but are excluded from the index upon recrawl. New pages are not indexed.

Page not found. Search engines may keep it in the index for some time. Use 410 for faster removal.

Request method is not supported for this URL. For example, POST to a GET-only endpoint.

Client took too long to send the request — server closed the connection. May indicate hosting issues.

Page permanently deleted. Search engines remove it from the index faster than with 404 upon recrawl.

April Fools RFC joke status. The server refuses to brew coffee because it is a teapot. Never used in real websites.

Data received but contains logical errors — for example, invalid email in a form. Typical for APIs and forms.

Rate limit exceeded. Frequent occurrence reduces crawl rate and may stop search bots from scanning the site entirely.

Content blocked due to legal demand — court order, copyright, regional law. Not critical for SEO with legal justification, but may affect regional trust.

Client closed the connection before the server responded. Non-standard Nginx code — indicates a slow server or impatient user.

Page returns 200 OK but is actually empty or shows a 'nothing found' message. Google detects these pages and may choose not to index them.

Server error. One-time errors are usually ignored by search engines, but repeated occurrences may lead to the page being excluded from the index upon recrawl.

Server does not support the request method. Rarely seen on regular websites.

Proxy received an invalid response from the backend. Often occurs when PHP or the app behind Nginx crashes or is overloaded.

Server temporarily unavailable. Use the Retry-After header — without it, search engines may treat 503 as 500. Prolonged 503 threatens the index.

Proxy timed out waiting for the backend. Symptom of a slow database or overloaded server.

Server has insufficient storage to complete the request. Rare in regular web — specific to WebDAV.

Server detected an infinite loop while processing the request. WebDAV-specific, analogous to a redirect loop but at server level.

Network authentication required — for example, accepting terms on a public Wi-Fi captive portal. Search bots cannot pass this barrier.

Cloudflare received an unexpected response from the server. Search engines treat this as a 5xx error — negatively affects indexing and site availability.

Cloudflare cannot connect to the server — it is completely down. Search engines treat this as 5xx — site is unavailable for both users and crawlers.

Cloudflare timed out waiting for the server during TCP handshake. Search engines treat this as 5xx — server is overloaded or unreachable.

Cloudflare cannot reach the origin server — DNS missing, wrong IP, or server is offline. Treated by search engines as 5xx.

Connection established but server did not respond within 100 seconds. Symptom of heavy database queries or runaway scripts. Treated as 5xx.

Cloudflare cannot establish an SSL connection to the origin server. Invalid certificate or incompatible TLS settings on the host.

Certificate on the origin server is invalid or self-signed. Cloudflare does not trust it in Full (strict) mode.