Azure Storage CORS Ideas – Introduction – Half One

The web site sends the request a picture from It has requested to embed a picture despite the fact that cross-origin requests the browser won’t allow cross by default as a result of embedding a picture is an easy request. So the picture shall be embedded with this.

Within the browser, I’ve this demo web page setup to request a picture from the demo azure storage account as CORS enabled. This represents the instance for


Now open up the dev instruments let shut the console and examine the picture. You’ll be able to see right here it’s merely embedded.



Should you have a look at the community site visitors and reload the web page, we are able to see a single request goes out. See that within the under picture there isn’t a CORS header that has been set, however the request succeeds. 


Azure Storage CORS Concepts


The server enabled CORS restriction and disallow the request surprisingly the reply isn’t any. Because the browser merely requested, it won’t ship the origin header which is required for all CORS requests. The server may return CORS rule within the response header “Entry-Management-Enable-Origin”: 

Azure Storage CORS Concepts

However on this case, the browser not treating as CORS request will ignore any CORS header within the response. If we up into the Storage accounts within the Azure Portal you may see CORS already enabled for this demo account.


Azure Storage CORS Concepts


Let’s have a look at the response for this embedded picture from Azure. There isn’t a CORS associated header is on the response. That is due to the best way Azure responds to the request. Because the browser has not initiated the CORS request, Azure won’t return any CORS associated headers within the response.


Azure Storage CORS Concepts



All CORS requests should embrace the Origin header.


These are the headers when working with CORS.

  • AllowedOrigins – The Origin domains make a request in opposition to the storage service through CORS.

  • AllowedMethods – The strategies that the origin might use for CORS request. For instance, PUT and GET requests are permitted.

  • AllowedHeaders – The request headers that the origin area might specify on the characters.

  • ExposeHeaders -The response headers which may be despatched within the response to the CORS request and uncovered by the browser to the request issuer

  • MaxAgeInSeconds – The utmost period of time {that a} browser ought to cache the preflight OPTIONS request.

On this article, you could have realized CORS ideas in Azure storage. Within the subsequent article, we are going to see the CORS within the browser. Be happy to refill the remark field under when you want any additional help. 

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