Use Twilio's REST API to send faxes to your SIP-enabled endpoints. If you are unfamiliar with SIP, or want more information on how Twilio works with your SIP endpoint, please see the SIP overview.
Initiate SIP sessions via the REST API by POSTing to the same faxes resource used to initiate traditional fax sessions (see sending faxes for more information). For example, send a fax over SIP by POSTing to your account's fax list resource URI:
All outgoing fax features and parameters are supported -- the only difference is that you pass different values in the
From parameters. In the
To parameter, put the SIP URI you are trying to connect to. In the
From parameter, specify the user you want to show up in the
From header in the SIP request.
|To||The SIP URI to which you want to send the fax (📇 PII MTL: 120 days)|
To parameter specifies a SIP address for Twilio to connect to. The body of the URI element should be a valid SIP URI under 256 characters. For example:
Pass headers in the
To parameter by appending them to the end of the SIP URI. For certain helper libraries, "&" will need to be encoded as
%26 (please see the documentation for the library you are using). The total characters passed in a header must be under 1024. For example:
Set a parameter on your SIP URI to specify what transport protocol you want to use. Currently, this is limited to
UDP. By default, Twilio sends your SIP INVITE over
UDP. Change this by using the transport parameter:
|From||This value is used to populate the username portion of the From header that is passed to the SIP endpoint. This may be any alphanumeric character, as well as the plus, minus, underscore, and period characters (
|SipAuthUsername||Your authentication username (max 256 characters). (🏢 not PII)|
|SipAuthPassword||The password for the user (max 256 characters). (🏢 not PII)|
Send a Fax Using SIP.
Pass user and password for authentication.
Pass headers and parameters as part of the SIP URI.