MVC 5 prevents access to content via Iframe

Try something like this in Global.asax:

protected void Application_PreSendRequestHeaders(object sender, EventArgs e)
 {
   HttpContext.Current.Response.Headers.Remove("X-Frame-Options");
 }

EDIT:

Look at answer of Colin Bacon. It is more correct than mine.

In short - don't remove this header if you don't want to run your site in IFRAME because it will open forgery vulnerability. But if you still want to remove it - use AntiForgeryConfig.SuppressXFrameOptionsHeader = true; in Application_Start, it is more cleaner way for doing this.

MVC5 automatically adds the HTTP header X-Frame-Options with SAMEORIGIN. This prevents your site from being loaded into an iframe.

But we can turn this off in Application_Start in the Global.asax.cs.

Example

protected void Application_Start()
{
    AntiForgeryConfig.SuppressXFrameOptionsHeader = true;
}

Update

I have written a post about this MVC5 prevents your website being loaded in an IFRAME

If you want a little more flexibility, here's an ActionAttribute that adds/removes headers based on a whitelist. If the referrer isn't in the whitelist, then the SAMEORIGIN header is left in place. I was going to paste the code, but SO complains about the length.

https://long2know.com/2016/06/asp-net-anti-forgery-xframe-options/