Is "*" or the server's URI the default value for Access-Control-Allow-Origin header? If the header is not set, does it mean that every origin has access to the resource?
Cross-Origin Resource Sharing (CORS) is an HTTP-header-based tool that's used to locate other origin servers that an end user's browser can use to get your content.
What is the Access-Control-Allow-Origin response header? The Access-Control-Allow-Origin header is included in the response from one website to a request originating from another website, and identifies the permitted origin of the request.
The Access-Control-Allow-Headers response header is used in response to a preflight request which includes the Access-Control-Request-Headers to indicate which HTTP headers can be used during the actual request. This header is required if the request has an Access-Control-Request-Headers header.
Since the header is currently set to allow access only from https://yoursite.com , the browser will block access to the resource and you will see an error in your console. Now, to fix this, change the headers to this: res. setHeader("Access-Control-Allow-Origin", "*");
There is no default value.
If it isn't set, then it isn't set. If it is set, then it must have an explicit value.
If the header is not set, does it mean that every origin has access to the resource?
No. It means that the Same Origin Policy is enforced as normal. No origins are granted permission.
the server's URI
There is no reason to ever set the Access-Control-Allow-Origin
to be the server's own URL. Same Origin requests don't need permission from CORS.
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