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The send() method of the RTCDataChannel interface sends data across the data channel to the remote peer. This can be done any time except during the initial process of creating the underlying transport channel. Data sent before connecting is buffered if possible (or an error occurs if it's not possible), and is also buffered if sent while the connection is closing or closed.

Different browsers have different limitations on the size of the message you can send. Specifications exist to define how to automatically fragment large messages, but not all browsers implement them, and those that do have various additional restrictions. This will get less complicated over time, but for now, if you have questions, see Understanding message size limits in Using WebRTC data channels.




The data to transmit across the connection. This may be a USVString, a Blob, an ArrayBuffer, or an ArrayBufferView.

Return value



Since the data channel uses a separate transport channel from the media content, it must establish its own connection; if it hasn't finished doing so (that is, its readyState is "connecting"), this error occurs without sending or buffering the data.
The specified data would need to be buffered, and there isn't room for it in the buffer. In this scenario, the underlying transport is immediately closed.
The specified data is too large for the other peer to receive. Since there are multiple techniques for breaking up large data into smaller pieces for transfer, it's possible to encounter scenarios in which the other peer does not support the same ones. For example, if one peer is a modern browser that supports using the EOR (End of Record) flag to indicate when a received message is the last piece of a multi-part object sent using send(). For more information about message size restrictions, see Understanding message size limits in Using WebRTC data channels.


In this example, a routine called sendMessage() is created; it accepts an object as input and sends to the remote peer, over the RTCDataChannel, a JSON string with the specified object and a time stamp.

var pc = new RTCPeerConnection();
var dc = pc.createDataChannel("BackChannel");

function sendMessage(msg) {
  let obj = {
    "message": msg,
    "timestamp": new Date()


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

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support56 ? No No43 No
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support5656 ? No43 ?6.0

See also

Document Tags and Contributors

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