Buffers and Encoding

Binary data idioms with Buffer and encodings - the foundation for files, sockets, and crypto. Results appear in the same fence: same-line // comments when short, multiline // blocks below the sample when not.

Buffer from String

Create a buffer from text with an explicit encoding (default utf8).

const buf = Buffer.from("hello", "utf8");
buf.length        // 5
buf.toString()    // "hello"

alloc vs allocUnsafe

alloc zero-fills; allocUnsafe is faster but may contain old memory - overwrite before expose.

const safe = Buffer.alloc(4);
safe.equals(Buffer.from([0, 0, 0, 0]))  // true
const fast = Buffer.allocUnsafe(4);
fast.fill(0);
fast.length  // 4

Byte Length of String

Multibyte UTF-8 characters need more than string.length code units - use Buffer.byteLength.

const s = "café";
s.length                      // 4
Buffer.byteLength(s, "utf8")  // 5

Slice vs subarray

subarray (and legacy slice) share memory with the parent - mutating one affects the other.

const parent = Buffer.from("abcdef");
const view = parent.subarray(0, 3);
view[0] = 0x5a;  // "Z"
parent.toString()  // "Zbcdef"

Base64 Hex Encode

Convert binary to transport-safe strings and back.

const raw = Buffer.from([0xde, 0xad, 0xbe, 0xef]);
raw.toString("hex")      // "deadbeef"
raw.toString("base64")   // "3q2+7w=="
Buffer.from("deadbeef", "hex").equals(raw)  // true

Concat Buffers

Join chunks collected from a stream into one buffer.

const parts = [Buffer.from("a"), Buffer.from("b")];
Buffer.concat(parts).toString()  // "ab"
Buffer.concat(parts).length      // 2

Compare Buffers

Constant-time equality for secrets should use crypto.timingSafeEqual when lengths match.

import { timingSafeEqual } from "node:crypto";
const a = Buffer.from("token");
const b = Buffer.from("token");
timingSafeEqual(a, b)  // true
// lengths must match or timingSafeEqual throws

Read Write Integers

Read and write multi-byte integers at offsets for binary protocols.

const buf = Buffer.alloc(4);
buf.writeUInt32BE(0x12345678, 0);
buf.readUInt32BE(0).toString(16)  // "12345678"

TypedArray Interop

Buffers are Uint8Array views - share memory with TypedArrays carefully.

const buf = Buffer.from([1, 2, 3, 4]);
buf instanceof Uint8Array  // true
buf[0]  // 1

TextDecoder Encoder

Web-standard text encoding APIs work in Node for streams of strings.

const enc = new TextEncoder();
const dec = new TextDecoder("utf-8");
const bytes = enc.encode("hi");
dec.decode(bytes)  // "hi"
bytes.length       // 2

isBuffer Check

Detect Buffer instances when validating untrusted inputs.

import { Buffer } from "node:buffer";
Buffer.isBuffer(Buffer.from("x"))  // true
Buffer.isBuffer(Uint8Array.of(1))  // false

Fill and Copy

Fill a range or copy between buffers without string conversion.

const a = Buffer.alloc(4, 0);
const b = Buffer.from("xy");
b.copy(a, 1);
a.toString()  // "\0xy\0"  (nulls at ends)
a[1]          // 120  ("x")

URL Safe Base64

Prefer base64url for tokens in URLs (Node encoding support).

const tok = Buffer.from("payload").toString("base64url");
tok  // "cGF5bG9hZA"
Buffer.from(tok, "base64url").toString()  // "payload"

StringDecoder Streaming

Decode multibyte UTF-8 safely across chunk boundaries with StringDecoder.

import { StringDecoder } from "node:string_decoder";
const dec = new StringDecoder("utf8");
const euro = Buffer.from("€", "utf8");  // 3 bytes
dec.write(euro.subarray(0, 1)) + dec.write(euro.subarray(1))
// "€"  (empty first write, complete on second)

Blob and File

Web Blob is available for interop with fetch bodies and undici.

const blob = new Blob([Buffer.from("hi")], { type: "text/plain" });
blob.size  // 2
await blob.text()  // "hi"

Streams and Pipelines - buffers flowing through streams
Filesystem and Path - reading binary files
HTTP and Fetch - request and response bodies

Node.js API Documentation - Complete reference for core modules and APIs.
Node.js Learn Guides - Official learning path.
Stack Overflow – Node.js Tag - Q&A for real-world problems.
Node.js Cookbook, 5th Edition - Practical server-side recipes.
Node.js the Right Way - Server-side JavaScript fundamentals.

Stack versions: Node.js 24.18.0 (LTS line 24) · TypeScript 5.6+ · npm 10+

Reviewed by Chris St. John·Last updated Jul 18, 2026

Was this article helpful?

Reference Code Reference Buffer Encoding Binary

Buffers and Encoding

Buffer from String

Create a buffer from text with an explicit encoding (default utf8).

const buf = Buffer.from("hello", "utf8");
buf.length        // 5
buf.toString()    // "hello"

alloc vs allocUnsafe

alloc zero-fills; allocUnsafe is faster but may contain old memory - overwrite before expose.

const safe = Buffer.alloc(4);
safe.equals(Buffer.from([0, 0, 0, 0]))  // true
const fast = Buffer.allocUnsafe(4);
fast.fill(0);
fast.length  // 4

Byte Length of String

Multibyte UTF-8 characters need more than string.length code units - use Buffer.byteLength.

const s = "café";
s.length                      // 4
Buffer.byteLength(s, "utf8")  // 5

Slice vs subarray

subarray (and legacy slice) share memory with the parent - mutating one affects the other.

const parent = Buffer.from("abcdef");
const view = parent.subarray(0, 3);
view[0] = 0x5a;  // "Z"
parent.toString()  // "Zbcdef"

Base64 Hex Encode

Convert binary to transport-safe strings and back.

const raw = Buffer.from([0xde, 0xad, 0xbe, 0xef]);
raw.toString("hex")      // "deadbeef"
raw.toString("base64")   // "3q2+7w=="
Buffer.from("deadbeef", "hex").equals(raw)  // true

Concat Buffers

Join chunks collected from a stream into one buffer.

const parts = [Buffer.from("a"), Buffer.from("b")];
Buffer.concat(parts).toString()  // "ab"
Buffer.concat(parts).length      // 2

Compare Buffers

Constant-time equality for secrets should use crypto.timingSafeEqual when lengths match.

import { timingSafeEqual } from "node:crypto";
const a = Buffer.from("token");
const b = Buffer.from("token");
timingSafeEqual(a, b)  // true
// lengths must match or timingSafeEqual throws

Read Write Integers

Read and write multi-byte integers at offsets for binary protocols.

const buf = Buffer.alloc(4);
buf.writeUInt32BE(0x12345678, 0);
buf.readUInt32BE(0).toString(16)  // "12345678"

TypedArray Interop

Buffers are Uint8Array views - share memory with TypedArrays carefully.

const buf = Buffer.from([1, 2, 3, 4]);
buf instanceof Uint8Array  // true
buf[0]  // 1

TextDecoder Encoder

Web-standard text encoding APIs work in Node for streams of strings.

const enc = new TextEncoder();
const dec = new TextDecoder("utf-8");
const bytes = enc.encode("hi");
dec.decode(bytes)  // "hi"
bytes.length       // 2

isBuffer Check

Detect Buffer instances when validating untrusted inputs.

import { Buffer } from "node:buffer";
Buffer.isBuffer(Buffer.from("x"))  // true
Buffer.isBuffer(Uint8Array.of(1))  // false

Fill and Copy

Fill a range or copy between buffers without string conversion.

const a = Buffer.alloc(4, 0);
const b = Buffer.from("xy");
b.copy(a, 1);
a.toString()  // "\0xy\0"  (nulls at ends)
a[1]          // 120  ("x")

URL Safe Base64

Prefer base64url for tokens in URLs (Node encoding support).

const tok = Buffer.from("payload").toString("base64url");
tok  // "cGF5bG9hZA"
Buffer.from(tok, "base64url").toString()  // "payload"

StringDecoder Streaming

Decode multibyte UTF-8 safely across chunk boundaries with StringDecoder.

import { StringDecoder } from "node:string_decoder";
const dec = new StringDecoder("utf8");
const euro = Buffer.from("€", "utf8");  // 3 bytes
dec.write(euro.subarray(0, 1)) + dec.write(euro.subarray(1))
// "€"  (empty first write, complete on second)

Blob and File

Web Blob is available for interop with fetch bodies and undici.

const blob = new Blob([Buffer.from("hi")], { type: "text/plain" });
blob.size  // 2
await blob.text()  // "hi"

Streams and Pipelines - buffers flowing through streams
Filesystem and Path - reading binary files
HTTP and Fetch - request and response bodies

Node.js API Documentation - Complete reference for core modules and APIs.
Node.js Learn Guides - Official learning path.
Stack Overflow – Node.js Tag - Q&A for real-world problems.
Node.js Cookbook, 5th Edition - Practical server-side recipes.
Node.js the Right Way - Server-side JavaScript fundamentals.

Stack versions: Node.js 24.18.0 (LTS line 24) · TypeScript 5.6+ · npm 10+

Reviewed by Chris St. John·Last updated Jul 18, 2026

Was this article helpful?

Buffers and Encoding

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Buffers and Encoding