AJAX及API在IE10中异常，跨域请求Header问题求助

Hey Dylan, I’ve run into this exact IE10 quirk a few times—let’s walk through the most likely fixes since your backend is already configured correctly for modern browsers.

• Check for whitespace or formatting issues in your backend header
  IE10 is extremely strict about the format of Access-Control-Allow-Headers. If your backend returns the header with extra spaces (e.g., Access-Control-Allow-Headers: xxx, Content-Type instead of Access-Control-Allow-Headers: xxx,Content-Type) or inconsistent capitalization, IE10 will reject it. Double-check that the header value matches the exact name of your xxx request header, including case.

• Verify the OPTIONS preflight response in IE10
  Modern browsers handle CORS smoothly, but IE10 sometimes sends OPTIONS preflight requests with unexpected header formatting. Use a tool like Fiddler to capture the OPTIONS request from IE10 and confirm that the response’s Access-Control-Allow-Headers explicitly includes xxx. It’s possible your backend is returning the header for regular requests but not for OPTIONS preflights (some frameworks require explicit configuration for OPTIONS).

• Clear IE10’s CORS preflight cache
  IE10 aggressively caches the results of CORS preflight requests. If you recently added xxx to your allowed headers, IE10 might still be using an old cached response that doesn’t include it. Clear the browser’s cache completely, or add a Cache-Control: no-cache header to your OPTIONS response to prevent future caching issues.

• Ensure no proxy or middleware is modifying the header
  If you’re using a reverse proxy (like Nginx) or any middleware between your frontend and backend, it might be stripping or modifying the Access-Control-Allow-Headers header before it reaches IE10. Check your proxy configuration to make sure it’s passing through the header unchanged.

Hopefully one of these fixes gets your API working in IE10—let me know if you need to dig deeper into any of these steps!

内容的提问来源于stack exchange，提问作者Dylan