ArrayBuffer.prototype.byteLength

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.

The byteLength accessor property of ArrayBuffer instances returns the length (in bytes) of this array buffer.

Try it

// Create an ArrayBuffer with a size in bytes
const buffer = new ArrayBuffer(8);

// Use byteLength to check the size
const bytes = buffer.byteLength;

console.log(bytes);
// Expected output: 8

Description

The byteLength property is an accessor property whose set accessor function is undefined, meaning that you can only read this property. The value is established when the array is constructed and cannot be changed. This property returns 0 if this ArrayBuffer has been detached.

Examples

Using byteLength

js
const buffer = new ArrayBuffer(8);
buffer.byteLength; // 8

Specifications

Specification
ECMAScript® 2025 Language Specification
# sec-get-arraybuffer.prototype.bytelength

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobileserver
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
Deno
Node.js
byteLength

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Full support
Full support

See also