CORS In Action

Browsers such as Firefox 3.5 and above implement the W3C Cross-Origin Request Sharing (CORS) specification as a means to mitigate cross-site requests initiated by the XMLHttpRequest object in JavaScript as well as for web fonts. You can read more about Access Control at, including code snippets. Here you'll find some examples of the XMLHttpRequest API as a "container" for access control.

Four examples are given below. Simply "View Source" them to see how they work-- all JavaScript is resident within the XHTML. Full code listings showing the PHP scripts I used to handle requests (and formulate responses) will also be posted soonish. TXT dumps of the header exchanges between client and server are posted next to each example. Note that in keeping with the access control specification, Firefox 3.5 will always send the ORIGIN header when making requests mitigated by the CORS specification. The XMLHttpRequest object in Firefox 3.5 and beyond takes care of sending access-control headers; developers need to ensure that the resources they are accessing are sending the right headers back.