@msgpack/msgpack
Advanced tools
@msgpack/msgpack is an npm package that provides functionality for encoding and decoding data using the MessagePack format. MessagePack is a binary serialization format that is more efficient than JSON in terms of both size and speed. This package allows you to serialize JavaScript objects into a compact binary format and deserialize them back into JavaScript objects.
Encoding Data
This feature allows you to encode a JavaScript object into a MessagePack binary format. The `encode` function takes a JavaScript object and returns a Buffer containing the binary data.
const msgpack = require('@msgpack/msgpack');
const data = { foo: 'bar', num: 42 };
const encoded = msgpack.encode(data);
console.log(encoded);Decoding Data
This feature allows you to decode a MessagePack binary format back into a JavaScript object. The `decode` function takes a Buffer containing the binary data and returns the original JavaScript object.
const msgpack = require('@msgpack/msgpack');
const encoded = Buffer.from([0x82, 0xa3, 0x66, 0x6f, 0x6f, 0xa3, 0x62, 0x61, 0x72, 0xa3, 0x6e, 0x75, 0x6d, 0x2a]);
const decoded = msgpack.decode(encoded);
console.log(decoded);Custom Extension Types
This feature allows you to define custom extension types for encoding and decoding. You can use `addExtPacker` to specify how to serialize a custom type and `addExtUnpacker` to specify how to deserialize it.
const msgpack = require('@msgpack/msgpack');
class MyType {
constructor(value) {
this.value = value;
}
}
msgpack.addExtPacker(0x01, MyType, (obj) => msgpack.encode(obj.value));
msgpack.addExtUnpacker(0x01, (data) => new MyType(msgpack.decode(data)));
const myObj = new MyType('custom data');
const encoded = msgpack.encode(myObj);
const decoded = msgpack.decode(encoded);
console.log(decoded);msgpack-lite is another npm package for MessagePack serialization. It is designed to be lightweight and fast, with a focus on performance. Compared to @msgpack/msgpack, msgpack-lite may have fewer features but is optimized for speed and small bundle size.
notepack.io is a fast and small MessagePack implementation for JavaScript. It is designed to be highly efficient and is often used in performance-critical applications. Compared to @msgpack/msgpack, notepack.io is more focused on performance and may offer better speed at the cost of some additional features.
msgpack5 is a pure JavaScript implementation of the MessagePack format. It supports both encoding and decoding, as well as custom extension types. Compared to @msgpack/msgpack, msgpack5 offers similar functionality but may have different performance characteristics and API design.
This library is an implementation of MessagePack for TypeScript and JavaScript, providing a compact and efficient binary serialization format. Learn more about MessagePack at:
This library serves as a comprehensive reference implementation of MessagePack for JavaScript with a focus on accuracy, compatibility, interoperability, and performance.
Additionally, this is also a universal JavaScript library. It is compatible not only with browsers, but with Node.js or other JavaScript engines that implement ES2015+ standards. As it is written in TypeScript, this library bundles up-to-date type definition files (d.ts).
*Note that this is the second edition of "MessagePack for JavaScript". The first edition, which was implemented in ES5 and never released to npmjs.com, is tagged as classic.
import { deepStrictEqual } from "assert";
import { encode, decode } from "@msgpack/msgpack";
const object = {
nil: null,
integer: 1,
float: Math.PI,
string: "Hello, world!",
binary: Uint8Array.from([1, 2, 3]),
array: [10, 20, 30],
map: { foo: "bar" },
timestampExt: new Date(),
};
const encoded: Uint8Array = encode(object);
deepStrictEqual(decode(encoded), object);
encode(data: unknown, options?: EncoderOptions): Uint8Array
decode(buffer: ArrayLike<number> | BufferSource, options?: DecoderOptions): unknown
decodeMulti(buffer: ArrayLike<number> | BufferSource, options?: DecoderOptions): Generator<unknown, void, unknown>decodeAsync(stream: ReadableStreamLike<ArrayLike<number> | BufferSource>, options?: DecoderOptions): Promise<unknown>decodeArrayStream(stream: ReadableStreamLike<ArrayLike<number> | BufferSource>, options?: DecoderOptions): AsyncIterable<unknown>decodeMultiStream(stream: ReadableStreamLike<ArrayLike<number> | BufferSource>, options?: DecoderOptions): AsyncIterable<unknown>This library is published to npmjs.com as @msgpack/msgpack.
npm install @msgpack/msgpack
encode(data: unknown, options?: EncoderOptions): Uint8ArrayIt encodes data into a single MessagePack-encoded object, and returns a byte array as Uint8Array. It throws errors if data is, or includes, a non-serializable object such as a function or a symbol.
for example:
import { encode } from "@msgpack/msgpack";
const encoded: Uint8Array = encode({ foo: "bar" });
console.log(encoded);
If you'd like to convert an uint8array to a NodeJS Buffer, use Buffer.from(arrayBuffer, offset, length) in order not to copy the underlying ArrayBuffer, while Buffer.from(uint8array) copies it:
import { encode } from "@msgpack/msgpack";
const encoded: Uint8Array = encode({ foo: "bar" });
// `buffer` refers the same ArrayBuffer as `encoded`.
const buffer: Buffer = Buffer.from(encoded.buffer, encoded.byteOffset, encoded.byteLength);
console.log(buffer);
EncoderOptions| Name | Type | Default |
|---|---|---|
| extensionCodec | ExtensionCodec | ExtensionCodec.defaultCodec |
| context | user-defined | - |
| useBigInt64 | boolean | false |
| maxDepth | number | 100 |
| initialBufferSize | number | 2048 |
| sortKeys | boolean | false |
| forceFloat32 | boolean | false |
| forceIntegerToFloat | boolean | false |
| ignoreUndefined | boolean | false |
decode(buffer: ArrayLike<number> | BufferSource, options?: DecoderOptions): unknownIt decodes buffer that includes a MessagePack-encoded object, and returns the decoded object typed unknown.
buffer must be an array of bytes, which is typically Uint8Array or ArrayBuffer. BufferSource is defined as ArrayBuffer | ArrayBufferView.
The buffer must include a single encoded object. If the buffer includes extra bytes after an object or the buffer is empty, it throws RangeError. To decode buffer that includes multiple encoded objects, use decodeMulti() or decodeMultiStream() (recommended) instead.
for example:
import { decode } from "@msgpack/msgpack";
const encoded: Uint8Array;
const object = decode(encoded);
console.log(object);
NodeJS Buffer is also acceptable because it is a subclass of Uint8Array.
DecoderOptions| Name | Type | Default |
|---|---|---|
| extensionCodec | ExtensionCodec | ExtensionCodec.defaultCodec |
| context | user-defined | - |
| useBigInt64 | boolean | false |
| rawStrings | boolean | false |
| maxStrLength | number | 4_294_967_295 (UINT32_MAX) |
| maxBinLength | number | 4_294_967_295 (UINT32_MAX) |
| maxArrayLength | number | 4_294_967_295 (UINT32_MAX) |
| maxMapLength | number | 4_294_967_295 (UINT32_MAX) |
| maxExtLength | number | 4_294_967_295 (UINT32_MAX) |
| mapKeyConverter | MapKeyConverterType | throw exception if key is not string or number |
MapKeyConverterType is defined as (key: unknown) => string | number.
To skip UTF-8 decoding of strings, rawStrings can be set to true. In this case, strings are decoded into Uint8Array.
You can use max${Type}Length to limit the length of each type decoded.
decodeMulti(buffer: ArrayLike<number> | BufferSource, options?: DecoderOptions): Generator<unknown, void, unknown>It decodes buffer that includes multiple MessagePack-encoded objects, and returns decoded objects as a generator. See also decodeMultiStream(), which is an asynchronous variant of this function.
This function is not recommended to decode a MessagePack binary via I/O stream including sockets because it's synchronous. Instead, decodeMultiStream() decodes a binary stream asynchronously, typically spending less CPU and memory.
for example:
import { decode } from "@msgpack/msgpack";
const encoded: Uint8Array;
for (const object of decodeMulti(encoded)) {
console.log(object);
}
decodeAsync(stream: ReadableStreamLike<ArrayLike<number> | BufferSource>, options?: DecoderOptions): Promise<unknown>It decodes stream, where ReadableStreamLike<T> is defined as ReadableStream<T> | AsyncIterable<T>, in an async iterable of byte arrays, and returns decoded object as unknown type, wrapped in Promise.
This function works asynchronously, and might CPU resources more efficiently compared with synchronous decode(), because it doesn't wait for the completion of downloading.
This function is designed to work with whatwg fetch() like this:
import { decodeAsync } from "@msgpack/msgpack";
const MSGPACK_TYPE = "application/x-msgpack";
const response = await fetch(url);
const contentType = response.headers.get("Content-Type");
if (contentType && contentType.startsWith(MSGPACK_TYPE) && response.body != null) {
const object = await decodeAsync(response.body);
// do something with object
} else { /* handle errors */ }
decodeArrayStream(stream: ReadableStreamLike<ArrayLike<number> | BufferSource>, options?: DecoderOptions): AsyncIterable<unknown>It is alike to decodeAsync(), but only accepts a stream that includes an array of items, and emits a decoded item one by one.
for example:
import { decodeArrayStream } from "@msgpack/msgpack";
const stream: AsyncIterator<Uint8Array>;
// in an async function:
for await (const item of decodeArrayStream(stream)) {
console.log(item);
}
decodeMultiStream(stream: ReadableStreamLike<ArrayLike<number> | BufferSource>, options?: DecoderOptions): AsyncIterable<unknown>It is alike to decodeAsync() and decodeArrayStream(), but the input stream must consist of multiple MessagePack-encoded items. This is an asynchronous variant for decodeMulti().
In other words, it could decode an unlimited stream and emits a decoded item one by one.
for example:
import { decodeMultiStream } from "@msgpack/msgpack";
const stream: AsyncIterator<Uint8Array>;
// in an async function:
for await (const item of decodeMultiStream(stream)) {
console.log(item);
}
This function is available since v2.4.0; previously it was called as decodeStream().
Encoder and Decoder classes are provided to have better performance by reusing instances:
import { deepStrictEqual } from "assert";
import { Encoder, Decoder } from "@msgpack/msgpack";
const encoder = new Encoder();
const decoder = new Decoder();
const encoded: Uint8Array = encoder.encode(object);
deepStrictEqual(decoder.decode(encoded), object);
According to our benchmark, reusing Encoder instance is about 20% faster
than encode() function, and reusing Decoder instance is about 2% faster
than decode() function. Note that the result should vary in environments
and data structure.
Encoder and Decoder take the same options as encode() and decode() respectively.
To handle MessagePack Extension Types, this library provides ExtensionCodec class.
This is an example to setup custom extension types that handles Map and Set classes in TypeScript:
import { encode, decode, ExtensionCodec } from "@msgpack/msgpack";
const extensionCodec = new ExtensionCodec();
// Set<T>
const SET_EXT_TYPE = 0 // Any in 0-127
extensionCodec.register({
type: SET_EXT_TYPE,
encode: (object: unknown): Uint8Array | null => {
if (object instanceof Set) {
return encode([...object], { extensionCodec });
} else {
return null;
}
},
decode: (data: Uint8Array) => {
const array = decode(data, { extensionCodec }) as Array<unknown>;
return new Set(array);
},
});
// Map<K, V>
const MAP_EXT_TYPE = 1; // Any in 0-127
extensionCodec.register({
type: MAP_EXT_TYPE,
encode: (object: unknown): Uint8Array => {
if (object instanceof Map) {
return encode([...object], { extensionCodec });
} else {
return null;
}
},
decode: (data: Uint8Array) => {
const array = decode(data, { extensionCodec }) as Array<[unknown, unknown]>;
return new Map(array);
},
});
const encoded = encode([new Set<any>(), new Map<any, any>()], { extensionCodec });
const decoded = decode(encoded, { extensionCodec });
Ensure you include your extensionCodec in any recursive encode and decode statements!
Note that extension types for custom objects must be [0, 127], while [-1, -128] is reserved for MessagePack itself.
When you use an extension codec, it might be necessary to have encoding/decoding state to keep track of which objects got encoded/re-created. To do this, pass a context to the EncoderOptions and DecoderOptions:
import { encode, decode, ExtensionCodec } from "@msgpack/msgpack";
class MyContext {
track(object: any) { /*...*/ }
}
class MyType { /* ... */ }
const extensionCodec = new ExtensionCodec<MyContext>();
// MyType
const MYTYPE_EXT_TYPE = 0 // Any in 0-127
extensionCodec.register({
type: MYTYPE_EXT_TYPE,
encode: (object, context) => {
if (object instanceof MyType) {
context.track(object);
return encode(object.toJSON(), { extensionCodec, context });
} else {
return null;
}
},
decode: (data, extType, context) => {
const decoded = decode(data, { extensionCodec, context });
const my = new MyType(decoded);
context.track(my);
return my;
},
});
// and later
import { encode, decode } from "@msgpack/msgpack";
const context = new MyContext();
const encoded = encode({ myType: new MyType<any>() }, { extensionCodec, context });
const decoded = decode(encoded, { extensionCodec, context });
This library does not handle BigInt by default, but you have two options to handle it:
useBigInt64: true to map bigint to MessagePack's int64/uint64ExtensionCodec to map bigint to a MessagePack's extension typeuseBigInt64: true is the simplest way to handle bigint, but it has limitations:
So you might want to define a custom codec to handle bigint like this:
import { deepStrictEqual } from "assert";
import { encode, decode, ExtensionCodec, DecodeError } from "@msgpack/msgpack";
// to define a custom codec:
const BIGINT_EXT_TYPE = 0; // Any in 0-127
const extensionCodec = new ExtensionCodec();
extensionCodec.register({
type: BIGINT_EXT_TYPE,
encode(input: unknown): Uint8Array | null {
if (typeof input === "bigint") {
if (input <= Number.MAX_SAFE_INTEGER && input >= Number.MIN_SAFE_INTEGER) {
return encode(Number(input));
} else {
return encode(String(input));
}
} else {
return null;
}
},
decode(data: Uint8Array): bigint {
const val = decode(data);
if (!(typeof val === "string" || typeof val === "number")) {
throw new DecodeError(`unexpected BigInt source: ${val} (${typeof val})`);
}
return BigInt(val);
},
});
// to use it:
const value = BigInt(Number.MAX_SAFE_INTEGER) + BigInt(1);
const encoded = encode(value, { extensionCodec });
deepStrictEqual(decode(encoded, { extensionCodec }), value);
There is a proposal for a new date/time representations in JavaScript:
This library maps Date to the MessagePack timestamp extension by default, but you can re-map the temporal module (or Temporal Polyfill) to the timestamp extension like this:
import { Instant } from "@std-proposal/temporal";
import { deepStrictEqual } from "assert";
import {
encode,
decode,
ExtensionCodec,
EXT_TIMESTAMP,
encodeTimeSpecToTimestamp,
decodeTimestampToTimeSpec,
} from "@msgpack/msgpack";
// to define a custom codec
const extensionCodec = new ExtensionCodec();
extensionCodec.register({
type: EXT_TIMESTAMP, // override the default behavior!
encode(input: unknown): Uint8Array | null {
if (input instanceof Instant) {
const sec = input.seconds;
const nsec = Number(input.nanoseconds - BigInt(sec) * BigInt(1e9));
return encodeTimeSpecToTimestamp({ sec, nsec });
} else {
return null;
}
},
decode(data: Uint8Array): Instant {
const timeSpec = decodeTimestampToTimeSpec(data);
const sec = BigInt(timeSpec.sec);
const nsec = BigInt(timeSpec.nsec);
return Instant.fromEpochNanoseconds(sec * BigInt(1e9) + nsec);
},
});
// to use it
const instant = Instant.fromEpochMilliseconds(Date.now());
const encoded = encode(instant, { extensionCodec });
const decoded = decode(encoded, { extensionCodec });
deepStrictEqual(decoded, instant);
This will become default in this library with major-version increment, if the temporal module is standardized.
If there are large arrays of floating point numbers in your payload, there
is a way to decode it faster: define a custom extension type for Float#Array
with alignment.
An extension type's encode method can return a function that takes a parameter
pos: number. This parameter can be used to make alignment of the buffer,
resulting decoding it much more performant.
See an example implementation for Float32Array:
const extensionCodec = new ExtensionCodec();
const EXT_TYPE_FLOAT32ARRAY = 0; // Any in 0-127
extensionCodec.register({
type: EXT_TYPE_FLOAT32ARRAY,
encode: (object: unknown) => {
if (object instanceof Float32Array) {
return (pos: number) => {
const bpe = Float32Array.BYTES_PER_ELEMENT;
const padding = 1 + ((bpe - ((pos + 1) % bpe)) % bpe);
const data = new Uint8Array(object.buffer);
const result = new Uint8Array(padding + data.length);
result[0] = padding;
result.set(data, padding);
return result;
};
}
return null;
},
decode: (data: Uint8Array) => {
const padding = data[0]!;
const bpe = Float32Array.BYTES_PER_ELEMENT;
const offset = data.byteOffset + padding;
const length = data.byteLength - padding;
return new Float32Array(data.buffer, offset, length / bpe);
},
});
Blob is a binary data container provided by browsers. To read its contents when it contains a MessagePack binary, you can use Blob#arrayBuffer() or Blob#stream(). Blob#stream()
is recommended if your target platform support it. This is because streaming
decode should be faster for large objects. In both ways, you need to use
asynchronous API.
async function decodeFromBlob(blob: Blob): unknown {
if (blob.stream) {
// Blob#stream(): ReadableStream<Uint8Array> (recommended)
return await decodeAsync(blob.stream());
} else {
// Blob#arrayBuffer(): Promise<ArrayBuffer> (if stream() is not available)
return decode(await blob.arrayBuffer());
}
}
This library is compatible with the "August 2017" revision of MessagePack specification at the point where timestamp ext was added:
The living specification is here:
https://github.com/msgpack/msgpack
Note that as of June 2019 there're no official "version" on the MessagePack specification. See https://github.com/msgpack/msgpack/issues/195 for the discussions.
The following table shows how JavaScript values are mapped to MessagePack formats and vice versa.
The mapping of integers varies on the setting of useBigInt64.
The default, useBigInt64: false is:
| Source Value | MessagePack Format | Value Decoded |
|---|---|---|
| null, undefined | nil | null (*1) |
| boolean (true, false) | bool family | boolean (true, false) |
| number (53-bit int) | int family | number |
| number (64-bit float) | float family | number |
| string | str family | string (*2) |
| ArrayBufferView | bin family | Uint8Array (*3) |
| Array | array family | Array |
| Object | map family | Object (*4) |
| Date | timestamp ext family | Date (*5) |
| bigint | N/A | N/A (*6) |
null and undefined are mapped to nil (0xC0) type, and are decoded into nullrawStrings: true. In this case, strings are decoded into Uint8Array.ArrayBufferViews including NodeJS's Buffer are mapped to bin family, and are decoded into Uint8ArrayObject, it is regarded as Record<string, unknown> in terms of TypeScriptDate. This behavior can be overridden by registering -1 for the extension codec.useBigInt64: false mode, but you can define an extension codec for it.If you set useBigInt64: true, the following mapping is used:
| Source Value | MessagePack Format | Value Decoded |
|---|---|---|
| null, undefined | nil | null |
| boolean (true, false) | bool family | boolean (true, false) |
| number (32-bit int) | int family | number |
| number (except for the above) | float family | number |
| bigint | int64 / uint64 | bigint (*7) |
| string | str family | string |
| ArrayBufferView | bin family | Uint8Array |
| Array | array family | Array |
| Object | map family | Object |
| Date | timestamp ext family | Date |
This is a universal JavaScript library that supports major browsers and NodeJS.
TextEncoder and TextDecoder)ES2022 standard library used in this library can be polyfilled with core-js.
IE11 is no longer supported. If you'd like to use this library in IE11, use v2.x versions.
NodeJS v18 is required.
This module requires type definitions of AsyncIterator, ArrayBufferLike, whatwg streams, and so on. They are provided by "lib": ["ES2024", "DOM"] in tsconfig.json.
Regarding the TypeScript compiler version, only the latest TypeScript is tested in development.
Run-time performance is not the only reason to use MessagePack, but it's important to choose MessagePack libraries, so a benchmark suite is provided to monitor the performance of this library.
V8's built-in JSON has been improved for years, esp. JSON.parse() is significantly improved in V8/7.6, it is the fastest deserializer as of 2019, as the benchmark result bellow suggests.
However, MessagePack can handles binary data effectively, actual performance depends on situations. Esp. streaming-decoding may be significantly faster than non-streaming decoding if it's effective. You'd better take benchmark on your own use-case if performance matters.
Benchmark on NodeJS/v22.13.1 (V8/12.4)
| operation | op | ms | op/s |
|---|---|---|---|
| buf = Buffer.from(JSON.stringify(obj)); | 1348700 | 5000 | 269740 |
| obj = JSON.parse(buf.toString("utf-8")); | 1700300 | 5000 | 340060 |
| buf = require("msgpack-lite").encode(obj); | 591300 | 5000 | 118260 |
| obj = require("msgpack-lite").decode(buf); | 539500 | 5000 | 107900 |
| buf = require("@msgpack/msgpack").encode(obj); | 1238700 | 5000 | 247740 |
| obj = require("@msgpack/msgpack").decode(buf); | 1402000 | 5000 | 280400 |
| buf = /* @msgpack/msgpack */ encoder.encode(obj); | 1379800 | 5000 | 275960 |
| obj = /* @msgpack/msgpack */ decoder.decode(buf); | 1406100 | 5000 | 281220 |
Note that JSON cases use Buffer to emulate I/O where a JavaScript string must be converted into a byte array encoded in UTF-8, whereas MessagePack modules deal with byte arrays.
The NPM package distributed in npmjs.com includes both ES2015+ and ES5 files:
dist/ is compiled into ES2020 with CommomJS, provided for NodeJS v10dist.umd/ is compiled into ES5 with UMD
dist.umd/msgpack.min.js - the minified filedist.umd/msgpack.js - the non-minified filedist.esm/ is compiled into ES2020 with ES modules, provided for webpack-like bundlers and NodeJS's ESM-modeIf you use NodeJS and/or webpack, their module resolvers use the suitable one automatically.
This library is available via CDN:
<script crossorigin src="https://unpkg.com/@msgpack/msgpack"></script>
It loads MessagePack module to the global object.
You can use this module on Deno.
See example/deno-*.ts for examples.
deno.land/x is not supported.
You can use this module on Bun.
For simple testing:
npm run test
This library uses GitHub Actions.
Test matrix:
# run tests on NodeJS, Chrome, and Firefox
make test-all
# edit the changelog
code CHANGELOG.md
# bump version
npm version patch|minor|major
# run the publishing task
make publish
npm run update-dependencies
Copyright 2019 The MessagePack community.
This software uses the ISC license:
https://opensource.org/licenses/ISC
See LICENSE for details.
3.1.2 2025-05-25
https://github.com/msgpack/msgpack-javascript/compare/v3.1.1...v3.1.2
node --experimental-strip-typesFAQs
MessagePack for ECMA-262/JavaScript/TypeScript
The npm package @msgpack/msgpack receives a total of 749,242 weekly downloads. As such, @msgpack/msgpack popularity was classified as popular.
We found that @msgpack/msgpack demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
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