RTCPeerConnection.signalingState

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

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.

Note: 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.
Candidate Recommendation Initial specification.

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung Internet
Basic support
Experimental
Chrome Full support 56Edge Full support 15Firefox Full support 22IE ? Opera Full support 43
Notes
Full support 43
Notes
Notes Promise based version.
No support 37 — 43
Safari ? WebView Android Full support 56Chrome Android Full support 56Edge Mobile Full support YesFirefox Android Full support 44Opera Android Full support 43
Notes
Full support 43
Notes
Notes Promise based version.
No support 37 — 43
Safari iOS ? Samsung Internet Android Full support 6.0

Legend

Full support  
Full support
Compatibility unknown  
Compatibility unknown
Experimental. Expect behavior to change in the future.
Experimental. Expect behavior to change in the future.
See implementation notes.
See implementation notes.

See also

Document Tags and Contributors

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