CORS usability

CORS is supported by all modern browsers, and XDomainRequest is its equivalent in Internet Explorer 8 and 9. Your code may include a switch to provide both the methods.

Using CORS requires planning: what resource(s) do you need to access, and how will you use them in your application?

Executing CORS requires preparation:

1. You must place the CORS header Access-Control-Allow-Origin on the page(s) on your target domain(s) for CORS to succeed.

2. A best practice is making sure that AJAX is supported by the client; otherwise, CORS with JavaScript will not be possible, and the function making the request can fail silently. Provide a handler in case AJAX is not supported.

3. Preflight is required for non-simple CORS requests. Preflight can detect potential problems that can make the actual request fail and can provide better security.

Browser support for CORS

All modern browsers support CORS. You can check for support at .

Global CORS support: 88.84%

Global XDomainRequest (IE 8,9): 4.72%

Total global...