The RTCDTMFSender interface provides a mechanism for transmitting DTMF codes on a WebRTC RTCPeerConnection. You gain access to the connection's RTCDTMFSender through the RTCRtpSender.dtmf property on the audio track you wish to send DTMF with.

The primary purpose for WebRTC's DTMF support is to allow WebRTC-based communication clients to be connected to a public-switched telephone network (PSTN) or other legacy telephone service, including extant voice over IP (VoIP) services. For that reason, DTMF can't be used between two WebRTC-based devices, because there is no mechanism provided by WebRTC for receiving DTMF codes.


RTCDTMFSender.toneBuffer Read only

A DOMString which contains the list of DTMF tones currently in the queue to be transmitted (tones which have already been played are no longer included in the string). See toneBuffer for details on the format of the tone buffer.



Given a string describing a set of DTMF codes and, optionally, the duration of and inter-tone gap between the tones, insertDTMF() starts sending the specified tones. Calling insertDTMF() replaces any already-pending tones from the toneBuffer. You can abort sending queued tones by specifying an empty string ("") as the set of tones to play.


Listen to these events using addEventListener() or by assigning an event listener to the oneventname property of this interface.


The tonechange event is sent to the RTCDTMFSender instance's event handler to indicate that a tone has either started or stopped playing. Also available using the ontonechange event handler property.


See the article Using DTMF with WebRTC for a full example.


WebRTC 1.0: Real-Time Communication Between Browsers (WebRTC 1.0)
# rtcdtmfsender

Browser compatibility

BCD tables only load in the browser

See also