What is the common HTTP header for request by JS libs?

Question

Using the Prototype JavaScript framework I've noticed, that the Ajax requests are enriched with a header called X-Requested-With.

Do other JavaScript libraries like jQuery, dojo and YUI add headers to their Ajax requests? Is it always called X-Requested-With? Is this a standard?

The full header by Prototype:

X-Requested-With:     XMLHttpRequest
X-Prototype-Version:  1.5.0_rc0

Answer 1

The X-Requested-With header is sent by default by the following frameworks:

• Dojo
• ExtJS
• jQuery
• MooTools
• Node.js
• Prototype
• YUI

As usual, keep in mind that it is not mandatory for frameworks to send it, that sometimes the framework's user can override it, that client/firewall/proxy/server may affect it, and there are even known browser bug(s) for it.