The RTCConfiguration dictionary's optional certificates property is an array of RTCCertificate objects providing the security certificates available for use when authenticating duing the connection process.


let rtcConfiguration = {
  certificates: certificateList

let rtcConfiguration.certificates = [ cert1... ];
let certificates = rtcConfiguration.certificates;


An array of RTCCertificate objects, each specifying one security certificate available for use when connecting to a remote peer. If this property isn't specified, the browser will automatically generate and use a certificate to secure the connection.

See Using certificates below for more information on why you might want to—or not to—explicitly provide certificates.


If this property isn't included in the configuration, a set of certificates is automatically generated for each instance of RTCPeerConnection. Although a given DTLS connection only uses a single certificate, providing multiple options in the certificates list may improve the odds of establishing a connection by increasing the chances a mutually-compatible encryption algorithm and key size may be found.

The method by which a browser decides which certificate to use is implementation-dependent. Some browsers may choose the first listed certificate and ignore the rest of the list; others may take a different approach.

Using certificates

When you wish to provide your own certificates for use by an RTCPeerConnection instead of having the RTCPeerConnection generate them automatically, you do so by calling the static RTCPeerConnection.generateCertificate() function.

The certificates property's value cannot be changed once it's first specified. If it's included in the configuration passed into a call to a connection's setConfiguration(), it is ignored.

This attribute supports providing multiple certificates because even though a given DTLS connection uses only one certificate, providing multiple certificates allows support for multiple encryption algorithms. The implementation of RTCPeerConnection will choose which certificate to use based on the algorithms it and the remote peer support, as determined during DTLS handshake.

If you don't provide certificates, new ones are generated automatically. One obvious benefit to providing your own is identity key continuity—if you use the same certificate for subsequent calls, the remote peer can tell you're the same caller. This also avoids the cost of generating new keys.

<<<--- add link to information about identity --->>>


This example uses RTCPeerConnection.generateCertificate() to create a certificate, then uses it to open a new RTCPeerConnection.

    name: 'RSASSA-PKCS1-v1_5',
    hash: 'SHA-256',
    modulusLength: 2048,
    publicExponent: new Uint8Array([1, 0, 1])
}).then(function(cert) {
  var pc = new RTCPeerConnection({certificates: [cert]});


Specification Status Comment
The definition of 'RTCConfiguration.certificates' in that specification.
Candidate Recommendation Initial definition.

Browser compatibility

BCD tables only load in the browser