Cross-Origin Resource Sharing (CORS)
Cross-Origin Resource Sharing (CORS) is a security feature implemented by web browsers that prevents web pages from making requests to a different domain than the one that the web page is served from. This is known as the “same-origin policy”.
For example, if a web page is served from “https://example.com”, it will not be able to make requests to “https://other-domain.com” unless the server at “https://other-domain.com” explicitly allows it. This is done through the use of special HTTP headers, such as Access-Control-Allow-Origin, which specify which domains are allowed to make requests to the server.
CORS is a useful security feature, but it can sometimes cause problems for developers when trying to make cross-domain requests from their web pages. For example, if you are trying to make an AJAX request to a different domain, you may get an error like “No ‘Access-Control-Allow-Origin’ header is present on the requested resource”.
To overcome this issue, there are several approaches you can take. One option is to use a proxy server that sits between your web page and the target server, and adds the required Access-Control-Allow-Origin header to the server’s responses. This allows your web page to make requests to the proxy server, which in turn makes the actual request to the target server and passes the response back to your web page.
Another option is to enable CORS on the target server itself. This involves adding the Access-Control-Allow-Origin header to the server’s responses, and specifying which domains are allowed to make requests to the server. This allows your web page to make direct requests to the target server without the need for a proxy.
Finally, if you are using a modern web browser, you can use the fetch API to make cross-domain requests. The fetch API supports the CORS protocol, and will automatically add the required headers and handle the CORS negotiation with the target server. This allows you to make cross-domain requests without the need for a proxy or configuring the server.
In summary, CORS is a security feature that prevents web pages from making requests to a different domain than the one that the web page is served from. This can cause problems for developers trying to make cross-domain requests, but there are several approaches you can take to overcome this, such as using a proxy server, enabling CORS on the target server, or using the fetch API.