The CAPTCHA Forms protocol is specified in XEP-0158 (a Draft Standard of the XMPP Standards Foundation). This specification defines an XMPP protocol extension that entities may use to discover whether the sender of an XML stanza is a human user or a robot.

The following XML namespaces are used in the context of the CAPTCHA Forms protocol:

The following XML schemas are available for the CAPTCHA Forms protocol:

Information about this XMPP protocol is maintained by the XMPP Registrar.