100Continue
RFC 9110 §15.2.1Initial request received; client should proceed with the rest of request.
Developer Tip: Sent in response to Expect: 100-continue.
101Switching Protocols
RFC 9110 §15.2.2Server agrees to switch protocols (e.g. HTTP to WebSocket upgrade).
Developer Tip: Common in WebSocket handshakes.
Standard response for successful HTTP requests.
Developer Tip: The default success code for GET, PUT, or POST payloads.
201Created
RFC 9110 §15.3.2Request succeeded and a new resource was created.
Developer Tip: Always return the Location header with URL of newly created item.
204No Content
RFC 9110 §15.3.5Request succeeded, but no payload body is returned.
Developer Tip: Common for DELETE and pre-flight CORS OPTIONS responses.
301Moved Permanently
RFC 9110 §15.4.2Resource has permanently moved to a new URI specified in Location.
Developer Tip: Use for permanent SEO redirects. Search engines pass PageRank.
302Found (Temporary Redirect)
RFC 9110 §15.4.3Resource temporarily resides under a different URI.
Developer Tip: Search engines do not transfer link equity.
304Not Modified
RFC 9110 §15.4.5Cached copy is still fresh; no response body transferred.
Developer Tip: Saves network bandwidth. Triggered by If-None-Match or If-Modified-Since.
307Temporary Redirect
RFC 9110 §15.4.8Temporary redirect guaranteeing HTTP method does not mutate (e.g. POST remains POST).
Developer Tip: Preferred over 302 for non-idempotent form submissions.
308Permanent Redirect
RFC 9110 §15.4.9Permanent redirect guaranteeing HTTP method does not change.
Developer Tip: Preferred over 301 when preserving POST payloads permanently.
400Bad Request
RFC 9110 §15.5.1Malformed syntax, invalid parameters, or deceptively large request routing.
Developer Tip: Check JSON syntax, missing query parameters, or payload size limits.
401Unauthorized
RFC 9110 §15.5.2Authentication credentials are required or have expired/failed.
Developer Tip: Check Bearer token, session cookie, or Authorization header.
403Forbidden
RFC 9110 §15.5.4Client identity is known, but does not possess authorization privileges.
Developer Tip: Check role-based access control (RBAC), IP whitelisting, or firewall rules.
404Not Found
RFC 9110 §15.5.5Server cannot find the requested resource path.
Developer Tip: Verify routing endpoints, typo in URL path, or database ID existence.
405Method Not Allowed
RFC 9110 §15.5.6HTTP method used is not supported by target endpoint (e.g. POST on GET-only route).
Developer Tip: Check Allow header in response to see supported verbs.
409Conflict
RFC 9110 §15.5.10Request conflicts with current state of server resource (e.g. unique constraint).
Developer Tip: Common in version control conflicts or duplicate email registrations.
418I'm a teapot
RFC 2324 / RFC 7168RFC 2324 Hyper Text Coffee Pot Control Protocol easter egg.
Developer Tip: Used as an easter egg or anti-scraping honey pot.
422Unprocessable Content
RFC 9110 §15.5.21Syntax is valid JSON, but semantic instructions contain validation errors.
Developer Tip: Standard for form validation errors in modern REST APIs.
429Too Many Requests
RFC 6585 §4Rate limit exceeded; client has sent too many requests in given time window.
Developer Tip: Inspect Retry-After response header to know wait duration.
500Internal Server Error
RFC 9110 §15.6.1Uncaught backend exception or application crash.
Developer Tip: Check server application logs, unhandled promise rejections, and DB connections.
502Bad Gateway
RFC 9110 §15.6.3Reverse proxy / load balancer received invalid response from upstream origin.
Developer Tip: Origin Node/Python process may be down, restarting, or timing out behind Nginx/Cloudflare.
503Service Unavailable
RFC 9110 §15.6.4Server temporarily overloaded or down for maintenance.
Developer Tip: Check CPU/memory usage or scheduled maintenance scripts.
504Gateway Timeout
RFC 9110 §15.6.5Upstream server failed to respond within proxy timeout threshold.
Developer Tip: Increase proxy proxy_read_timeout or optimize slow database queries.
