Getting CORS to work on C# WebAPI

There are many guides for this, and it should be a simple thing, but there is one possible complication: duplicate header entries.

So I’ll make this quick. Refer to for more information.

“Where can I get System.Web.Http.Cors?”


“How do I enable CORS?”

Add to WebApiConfig.Register():


But now, depending on your other settings, you might get a duplicate Access-Control-Allow-Origin header. This is how you remove it:

Add to WebApiApplication in Global.asax.cs:


That’s it. Should work now.


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