RTCPeerConnection.signalingState

This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the specification changes.

The read-only signalingState property on the RTCPeerConnection interface returns one of the string values specified by the RTCSignalingState enum; these values describe the state of the signaling process on the local end of the connection while connecting or reconnecting to another peer. See "Signaling" in Lifetime of a WebRTC session for more details about the signaling process.

Because the signaling process is a state machine, being able to verify that your code is in the expected state when messages arrive can help avoid unexpected and avoidable failures. For example, if you receive an answer while the signalingState isn't "have-local-offer", you know that something is wrong, since you should only receive answers after creating an offer but before an answer has been received and passed into RTCPeerConnection.setLocalDescription(). Your code will be more reliable if you watch for mismatched states like this and handle them gracefully.

This value may also be useful during debugging, for example.

In addition, when the value of this property changes, a signalingstatechange event is sent to the RTCPeerConnection instance.

Syntax

 var state = RTCPeerConnection.signalingState;

Value

The allowed values are those included in the enum RTCSignalingState.

RTCSignalingState enum

The RTCSignalingState enum specifies the possible values of RTCPeerConnection.signalingState, which indicates where in the process of signaling the exchange of offer and answer the connection currently is.

Constant Description
"stable" There is no ongoing exchange of offer and answer underway. This may mean that the RTCPeerConnection object is new, in which case both the localDescription and remoteDescription are null; it may also mean that negotiation is complete and a connection has been established.
"have-local-offer" The local peer has called RTCPeerConnection.setLocalDescription(), passing in SDP representing an offer (usually created by calling RTCPeerConnection.createOffer()), and the offer has been applied successfully.
"have-remote-offer" The remote peer has created an offer and used the signaling server to deliver it to the local peer, which has set the offer as the remote description by calling RTCPeerConnection.setRemoteDescription().
"have-local-pranswer" The offer sent by the remote peer has been applied and an answer has been created (usually by calling RTCPeerConnection.createAnswer()) and applied by calling RTCPeerConnection.setLocalDescription(). This provisional answer describes the supported media formats and so forth, but may not have a complete set of ICE candidates included. Further candidates will be delivered separately later.
"have-remote-pranswer" A provisional answer has been received and successfully applied in response to an offer previously sent and established by calling setLocalDescription().
"closed"

The connection is closed.

This value moved into the RTCPeerConnectionState enum in the May 13, 2016 draft of the specification, as it reflects the state of the RTCPeerConnection, not the signaling connection. You now detect a closed connection by checking for connectionState to be "closed" instead.

Example

var pc = new RTCPeerConnection(configuration);
var state = pc.signalingState;

Specifications

Specification Status Comment
WebRTC 1.0: Real-time Communication Between Browsers
The definition of 'RTCPeerConnection.signalingState' in that specification.		 Working Draft Initial specification.

Browser compatibility

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari
Basic support (Yes)[1] (Yes) 22 (22) [2] No support (Yes) ?
Feature Android Webview Chrome for Android Edge Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support (Yes)[1] (Yes)[1] (Yes) 22.0 (22) [2] No support ? ?

[1] Though this property is not prefixed, the interface it belongs to was until Chrome 56.

[2] Though this property is not prefixed, the RTCPeerConnection interface it's a member of was until Firefox 44.

See also

Document Tags and Contributors

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 Contributors to this page: jpmedley, abbycar, Sheppy, teoli, wesj
 Last updated by: jpmedley,