node:buffer module APIs

While, the Buffer object is available as a global, there are additional Buffer-related APIs that are available only via the node:buffer module accessed using require('node:buffer').

buffer.atob(data): string

Decodes a string of Base64-encoded data into bytes, and encodes those bytes into a string using Latin-1 (ISO-8859-1).

The data may be any JavaScript-value that can be coerced into a string.

This function is only provided for compatibility with legacy web platform APIs and should never be used in new code, because they use strings to represent binary data and predate the introduction of typed arrays in JavaScript. For code running using Node.js APIs, converting between base64-encoded strings and binary data should be performed using Buffer.from(str, 'base64') and buf.toString('base64').

An automated migration is available (source:

npx codemod@latest @nodejs/buffer-atob-btoa

buffer.btoa(data): string

Decodes a string into bytes using Latin-1 (ISO-8859), and encodes those bytes into a string using Base64.

The data may be any JavaScript-value that can be coerced into a string.

This function is only provided for compatibility with legacy web platform APIs and should never be used in new code, because they use strings to represent binary data and predate the introduction of typed arrays in JavaScript. For code running using Node.js APIs, converting between base64-encoded strings and binary data should be performed using Buffer.from(str, 'base64') and buf.toString('base64').

An automated migration is available (source:

npx codemod@latest @nodejs/buffer-atob-btoa

buffer.isAscii(input): boolean

This function returns true if input contains only valid ASCII-encoded data, including the case in which input is empty.

A detached ArrayBuffer, or a TypedArray backed by one, is treated as empty.

buffer.isUtf8(input): boolean

This function returns true if input contains only valid UTF-8-encoded data, including the case in which input is empty.

A detached ArrayBuffer, or a TypedArray backed by one, is treated as empty.

Returns the maximum number of bytes that will be returned when buf.inspect() is called. This can be overridden by user modules. See util.inspect() for more details on buf.inspect() behavior.

An alias for buffer.constants.MAX_LENGTH.

An alias for buffer.constants.MAX_STRING_LENGTH.

buffer.resolveObjectURL(id): Blob

Resolves a 'blob:nodedata:...' an associated Blob object registered using a prior call to URL.createObjectURL().

buffer.transcode(source, fromEnc, toEnc): Buffer

Re-encodes the given Buffer or Uint8Array instance from one character encoding to another. Returns a new Buffer instance.

Throws if the fromEnc or toEnc specify invalid character encodings or if conversion from fromEnc to toEnc is not permitted.

Encodings supported by buffer.transcode() are: 'ascii', 'utf8', 'utf16le', 'ucs2', 'latin1', and 'binary'.

The transcoding process will use substitution characters if a given byte sequence cannot be adequately represented in the target encoding. For instance:

import { Buffer, transcode } from 'node:buffer';

const newBuf = transcode(Buffer.from('€'), 'utf8', 'ascii');
console.log(newBuf.toString('ascii'));
// Prints: '?'

const { Buffer, transcode } = require('node:buffer');

const newBuf = transcode(Buffer.from('€'), 'utf8', 'ascii');
console.log(newBuf.toString('ascii'));
// Prints: '?'

Because the Euro (€) sign is not representable in US-ASCII, it is replaced with ? in the transcoded Buffer.

On 32-bit architectures, this value is equal to 2³¹ - 1 (about 2 GiB).

On 64-bit architectures, this value is equal to Number.MAX_SAFE_INTEGER (2⁵³ - 1, about 8 PiB).

It reflects v8::Uint8Array::kMaxLength under the hood.

This value is also available as buffer.kMaxLength.

Represents the largest length that a string primitive can have, counted in UTF-16 code units.

This value may depend on the JS engine that is being used.