W3cubDocs

/Web APIs

WebSocket: binaryType property

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since ⁨July 2015⁩.

Note: This feature is available in Web Workers.

The WebSocket.binaryType property controls the type of binary data being received over the WebSocket connection.

Value

A string:

"blob"

Use Blob objects for binary data. This is the default value.

"arraybuffer"

Use ArrayBuffer objects for binary data.

Examples

// Create WebSocket connection.
const socket = new WebSocket("ws://localhost:8080");

// Change binary type from "blob" to "arraybuffer"
socket.binaryType = "arraybuffer";

// Listen for messages
socket.addEventListener("message", (event) => {
  if (event.data instanceof ArrayBuffer) {
    // binary frame
    const view = new DataView(event.data);
    console.log(view.getInt32(0));
  } else {
    // text frame
    console.log(event.data);
  }
});

Specifications

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Opera Safari Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet WebView Android WebView on iOS
binaryType 15 12 11 12.1 6 18 14 12.1 6 1.0 4.4 6

© 2005–2025 MDN contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/API/WebSocket/binaryType