---
title: RTCDataChannel.bufferedAmount
slug: Web/API/RTCDataChannel/bufferedAmount
tags:
  - Property
  - RTCDataChannel
  - Read-only
  - Reference
  - WebRTC
  - bufferedAmount
browser-compat: api.RTCDataChannel.bufferedAmount
---
{{APIRef("WebRTC")}}

The read-only `RTCDataChannel` property
**`bufferedAmount`** returns the number of bytes of data
currently queued to be sent over the data channel. The queue may build up as a
result of calls to the {{domxref("RTCDataChannel.send", "send()")}} method. This only
includes data buffered by the user agent itself; it doesn't include any framing overhead
or buffering done by the operating system or network hardware.

The user agent may implement the process of actually sending data in any way it
chooses; this may be done periodically during the event loop or truly asynchronously. As
messages are actually sent, this value is reduced accordingly.

> **Note:** Closing the data channel doesn't reset this count, even though the user agent purges
> the queued messages. However, even after closing the channel, attempts to send
> messages continue to add to the `bufferedAmount` value, even though the
> messages are neither sent nor buffered.

Whenever this value decreases to fall to or below the value specified in the
{{domxref("RTCDataChannel.bufferedAmountLowThreshold", "bufferedAmountLowThreshold")}}
property, the user agent fires the {{DOMxRef("RTCDataChannel.bufferedamountlow_event", "bufferedamountlow")}} event. This event may
be used, for example, to implement code which queues more messages to be sent whenever
there's room to buffer them.

## Syntax

```js
var amount = aDataChannel.bufferedAmount;
```

### Value

The number of bytes of data currently queued to be sent over the data channel but have
not yet been sent.

## Example

The snippet below includes a function which changes the contents of a block with the ID
"bufferSize" to a string indicating the number of bytes currently buffered on an
{{domxref("RTCDataChannel")}}.

    var dc = peerConnection.createDataChannel("File Transfer");

    /* ... */

    function showBufferedAmount(channel) {
      let el = document.getElementById("bufferSize");

      el.innerHTML = channel.bufferedAmount + " bytes";
    }

## Specifications

{{Specifications}}

## Browser compatibility

{{Compat}}

## See also

- [WebRTC](/en-US/docs/Web/API/WebRTC_API)
- [Using WebRTC data
  channels](/en-US/docs/Web/API/WebRTC_API/Using_data_channels)
- {{domxref("RTCDataChannel")}}
- {{domxref("RTCDataChannel.bufferedAmountLowThreshold")}}
- {{DOMxRef("RTCDataChannel.bufferedamountlow_event", "bufferedamountlow")}} event
- {{domxref("RTCDataChannel.onbufferedamountlow")}}
