HTTP

Hypertext Transfer Protocol

• HTTP is an application-layer protocol for transmitting hypermedia documents, such as HTML.

• HTTP follows a classical client-server model, with a client opening a connection to make a request, then waiting until it receives a response from the server.

• HTTP is a stateless protocol, meaning that the server does not keep any data (state) between two requests.

HTTP | MDN

HTTP headers

let the client and the server pass additional information with an HTTP request or response

• Request headers - contain more information about the resource to be fetched, or about the client requesting the resource.

• Response headers - hold additional information about the response, like its location or about the server providing it.

• Representation headers - contain information about the body of the resource, like its MIME type, or encoding/compression applied.

• Payload headers - contain representation-independent information about payload data, including content length and the encoding used for transport.

HTTP headers - HTTP | MDN

HTTP request methods

indicate the desired action to be performed for a given resource

Although they can also be nouns, these request methods are sometimes referred to as HTTP verbs.

Verbs	Description
GET	The GET method requests a representation of the specified resource. Requests using GET should only retrieve data.
POST	The POST method submits an entity to the specified resource, often causing a change in state on the server.
PUT	The PUT method replaces all current representations of the target resource with the request payload.
DELETE	The DELETE method deletes the specified resource.
PATCH	The PATCH method applies partial modifications to a resource.

All methods are , as well as PUT and DELETE. The POST method is not idempotent.

HTTP request methods - HTTP | MDN

HTTP response status codes

indicate whether a specific HTTP request has been successfully completed

Class	Codes	Description
1xx		Information reponses
2xx		Successful responses
	200	OK
	201	Created
	204	No Content
	205	Reset Content
3xx		Redirection messages
	300	Multiple Choices
	301	Moved Permanently
	302	Found
4xx		Client-error responses
	400	Bad Request
	401	Unauthorized
	403	Forbidden
	404	Not Found
	429	Too Many Requests
5xx		Server-error responses
	500	Internal Server Error
	502	Bad Gateway
	503	Service Unavailable
	504	Gateway Timeout

HTTP response status codes - HTTP | MDN