This content originally appeared on DEV Community and was authored by Hyunjin Cho
*CORS *
Cross-Origin Resource Sharing
a HTTP header based mechanism used when requesting resource to another origin from an origin
origin : like address for server
protocol : https://
host : google.com
port : :80
the system that compare origins is activated under browser. That is, when the server receives the request from another origin, the server sends response unless there is a restriction that the server will take request from same origin. Then, browser will compare the response whether CORS is violated or not.
browser : https://hyunin.com
server : https://server.com
- send request to server
- send response to the browser
- the browser check if the origin is different or not. If different, the response is thrown.
Because of that, this CORS does not work between server communication.
Working of CORS
when requesting resources from another origin, the application-browser- use HTTP protocol and the request header includes Origin with value
Origin: https://hyunjin.com
then when the server send response, the response header includes Access-Control-Allow-Origin with allowed value. The browser will compare ACAO and request origin
1. when requesting preflight
preflight means the pre-request before actual request for checking if it is safe to send request. For this, OPTIONS method is used.
browser send pre-request(OPTIONS/resources - Origin:https://hyunjin.com) to the server
the server send response(200 ok Access-Control-Allow-Origin: *) to the browser.
browser send actual request to the server
the server send response
more specifically,
In preflight,
there are origin, Access-Control-Request-headers, Access-Control-Request-Method
In the response to the preflight,
there are Access-Control-Allow-Origin
2. simple request
No preflight and others are same
the condition for this,
- the request method should be one of GET, HEAD, POST
- only Accept, Accept-Language, Content-Language, Content-Type, DPR, Downlink, Save-Data, Viewport-Width, Width should be used
- when content-type, application/x-www-form-urlencoded, multipart/form-data, text/plain
resource: https://evan-moon.github.io/2020/05/21/about-cors/
This content originally appeared on DEV Community and was authored by Hyunjin Cho
Hyunjin Cho | Sciencx (2022-04-05T20:59:41+00:00) April 5th, 2022. Retrieved from https://www.scien.cx/2022/04/05/april-5th-2022-2/
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