RCML is a set of instructions you can use to tell Restcomm what to do when you receive an incoming call or SMS.

When someone makes a call or sends an SMS to one of your Restcomm numbers#, Restcomm will look up the URL associated with that phone number and make a request to that URL. Restcomm will read RCML instructions at that URL to determine what to do: record the call#, play a message for the caller#, prompt the caller to press digits on their keypad#, etc.

For example#, the following will say a short message#, and then record the caller’s voice:

<?xml version="1.0" encoding="UTF-8"?>
    <Say voice="woman">Please leave a message after the tone.</Say>
    <Record maxLength="20" />

RCML is similar to HTML. Only one RCML document is rendered to the caller at once#, but many documents can be linked together to build complex interactive voice applications.

Calls from a Restcomm number to an outside number are controlled using RCML in the same manner as incoming calls. The initial URL for the call is provided as a parameter to the Restcomm REST API request you make to initiate the call.

How Restcomm Interacts with Your Application