The RTCSessionDescription interface describes one end of a connection—or potential connection—and how it's configured. Each RTCSessionDescription consists of a description type indicating which part of the offer/answer negotiation process it describes and of the SDP descriptor of the session.

The process of negotiating a connection between two peers involves exchanging RTCSessionDescription objects back and forth, with each description suggesting one combination of connection configuration options that the sender of the description supports. Once the two peers agree upon a configuration for the connection, negotiation is complete.

Instance properties

The RTCSessionDescription interface doesn't inherit any properties.

RTCSessionDescription.type Read only

An enum describing the session description's type.

RTCSessionDescription.sdp Read only

A string containing the SDP describing the session.

Instance methods

The RTCSessionDescription doesn't inherit any methods.

RTCSessionDescription() Deprecated

This constructor returns a new RTCSessionDescription. The parameter is a RTCSessionDescriptionInit dictionary containing the values to assign the two properties.


Returns a JSON description of the object. The values of both properties, type and sdp, are contained in the generated JSON.


signalingChannel.onmessage = (evt) => {
  if (!pc) start(false);

  const message = JSON.parse(evt.data);
  if (message.sdp) {
      new RTCSessionDescription(message),
      () => {
        // if we received an offer, we need to answer
        if (pc.remoteDescription.type === "offer") {
          pc.createAnswer(localDescCreated, logError);
  } else {
      new RTCIceCandidate(message.candidate),
      () => {},


WebRTC: Real-Time Communication in Browsers
# rtcsessiondescription-class

Browser compatibility

BCD tables only load in the browser

See also