W3cubDocs

/DOM

RTCSessionDescription

This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

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.

Properties

The RTCSessionDescription interface doesn't inherit any properties.

RTCSessionDescription.type Read only: An enum of type RTCSdpType describing the session description's type.

RTCSessionDescription.sdp Read only: A DOMString containing the SDP describing the session.

Constants

RTCSdpType

This enum defines strings that describe the current state of the session description, as used in the type property. The session description's type will be specified using one of these values.

Value	Description
`answer`	The SDP contained in the `sdp` property is the definitive choice in the exchange. In other words, this session description describes the agreed-upon configuration, and is being sent to finalize negotiation.
`offer`	The session description object describes the initial proposal in an offer/answer exchange. The session negotiation process begins with an offer being sent from the caller to the callee.
`pranswer`	The session description object describes a provisional answer; that is, it's a response to a previous offer or provisional answer.
`rollback`	This special type with an empty session description is used to roll back to the previous stable state.

Methods

The RTCSessionDescription doesn't inherit any methods.

RTCSessionDescription(): This constructor returns a new RTCSessionDescription. The parameter is a RTCSessionDescriptionInit dictionary containing the values to assign the two properties.
RTCSessionDescription.toJSON(): Returns a JSON description of the object. The values of both properties, type and sdp, are contained in the generated JSON.

Example

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

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

Specifications

Specification	Status	Comment
WebRTC 1.0: Real-time Communication Between Browsers The definition of 'RTCSessionDescription' in that specification.	Candidate Recommendation	Initial definition.

Browser compatibilityUpdate compatibility data on GitHub

	Desktop
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari
Basic support	Yes	Yes	Yes Prefixed Yes Prefixed Prefixed Requires the vendor prefix: -moz-	No	?	?
`type`	Yes	15	Yes Prefixed Yes Prefixed Prefixed Requires the vendor prefix: -moz-	No	?	?
`sdp`	Yes	15	Yes Prefixed Yes Prefixed Prefixed Requires the vendor prefix: -moz-	No	?	?
`RTCSessionDescription()` constructor	Yes	Yes	Yes Prefixed Yes Prefixed Prefixed Requires the vendor prefix: -moz-	No	?	?
`toJSON`	Yes	15	Yes Prefixed Yes Prefixed Prefixed Requires the vendor prefix: -moz-	No	?	?

	Mobile
	Android webview	Chrome for Android	Edge Mobile	Firefox for Android	Opera for Android	iOS Safari	Samsung Internet
Basic support	Yes	Yes	Yes	?	?	?	Yes
`type`	Yes	Yes	Yes	?	?	?	Yes
`sdp`	Yes	Yes	Yes	?	?	?	Yes
`RTCSessionDescription()` constructor	Yes	Yes	Yes	?	?	?	Yes
`toJSON`	Yes	Yes	Yes	?	?	?	Yes