HTTP Status Codes & Methods

1xx: informational 2xx: success 3xx: redirection 4xx: client error 5xx: server error

200

201

204

301 Moved Permanently: the resource has a new permanent URL (search engines transfer ranking). 302 Found: a temporary redirect.

304

400

401: you are not authenticated (missing or invalid credentials); logging in may help. 403: the server knows who you are, but you do not have permission.

404

405

409

422

429

500

502 Bad Gateway: a proxy got an invalid response from the upstream server. 503 Service Unavailable: the server is overloaded or down for maintenance. 504 Gateway Timeout: a proxy did not get a response from upstream in time.

GET: read a resource POST: create a resource or trigger an action PUT: replace a resource entirely PATCH: partially update a resource DELETE: remove a resource

PUT sends the complete new representation and replaces the resource. PATCH sends only the fields to change.

GET, HEAD, OPTIONS, PUT and DELETE. Repeating the same request has the same effect as sending it once.

GET, HEAD and OPTIONS: they should not change server state.

Before certain cross-origin requests (e.g. with custom headers or methods like PUT), the browser sends an OPTIONS request asking whether the server allows it, via Access-Control-Allow-* headers.

Each request is independent; the server does not remember previous ones. Apps send state with every request, using cookies (session IDs) or tokens such as JWTs in the Authorization header.