pbf

A low-level, fast, ultra-lightweight (2.5KB gzipped) JavaScript library for decoding and encoding protocol buffers, a compact binary format for structured data serialization. Works both in Node and the browser. Supports lazy decoding and detailed customization of the reading/writing code.

Performance

This library is fast — competitive with or faster than other JS protobuf implementations — while being an order of magnitude smaller. Here's a result from a real-world benchmark on Node v26 (decoding and encoding 439 Mapbox vector tiles, 37.5 MB total; the equivalent JSON is 136 MB):

JSON throughput is measured against the 136 MB JSON payload, not the 37.5 MB pbf payload — on the same data, pbf is ~2× faster to decode and ~2.5× faster to encode, and produces output roughly a quarter the size. See bench/bench-tiles.js.

Examples

Using Compiled Code

Install pbf and compile a JavaScript module from a .proto file:

$ npm install -g pbf
$ pbf example.proto > example.js

Then read and write objects using the module like this:

import {PbfReader, PbfWriter} from 'pbf';
import {readExample, writeExample} from './example.js';

// read
const obj = readExample(new PbfReader(buffer));

// write
const pbf = new PbfWriter();
writeExample(obj, pbf);
const buffer = pbf.finish();

Alternatively, you can compile a protobuf schema file directly in the code:

import {compile} from 'pbf/compile';
import schema from 'protocol-buffers-schema';

const proto = schema.parse(fs.readFileSync('example.proto'));
const {readExample, writeExample} = compile(proto);

Custom Reading

const pbf = new PbfReader(buffer);
const data = readData(pbf);

function readData(pbf, end) {
    const data = {};
    let field;
    while ((field = pbf.nextField(end))) {
        if (field === 1) data.name = pbf.readString();
        else if (field === 2) data.version = pbf.readVarint();
        else if (field === 3) data.layer = readLayer(pbf, pbf.readVarint() + pbf.pos);
    }
    return data;
}
function readLayer(pbf, end) {
    const layer = {};
    let field;
    while ((field = pbf.nextField(end))) {
        if (field === 1) layer.name = pbf.readString();
        else if (field === 3) layer.size = pbf.readVarint();
    }
    return layer;
}

Custom Writing

const pbf = new PbfWriter();
writeData(data, pbf);
const buffer = pbf.finish();

function writeData(data, pbf) {
    pbf.writeStringField(1, data.name);
    pbf.writeVarintField(2, data.version);
    pbf.writeMessage(3, writeLayer, data.layer);
}
function writeLayer(layer, pbf) {
    pbf.writeStringField(1, layer.name);
    pbf.writeVarintField(2, layer.size);
}

Install

Install using NPM with npm install pbf, then import as a module:

import {PbfReader, PbfWriter} from 'pbf';

Or use as a module directly in the browser with jsDelivr:

<script type="module">
    import {PbfReader, PbfWriter} from 'https://cdn.jsdelivr.net/npm/pbf/+esm';
</script>

Alternatively, there's a browser bundle exposing a Pbf global with PbfReader and PbfWriter properties:

<script src="https://cdn.jsdelivr.net/npm/pbf"></script>

API

The library exposes two classes: PbfReader for decoding and PbfWriter for encoding. Splitting them lets bundlers tree-shake the half you don't use.

Create a PbfReader from a Buffer or Uint8Array:

// parse a pbf file from disk in Node
const pbf = new PbfReader(fs.readFileSync('data.pbf'));

// parse a pbf file in a browser after an ajax request with responseType="arraybuffer"
const pbf = new PbfReader(new Uint8Array(xhr.response));

Both classes expose the following properties:

pbf.length; // length of the underlying buffer
pbf.pos; // current offset for reading or writing

Reading

Loop over a message's fields with nextField and dispatch on the field number. Unrecognized or unread fields are skipped automatically on the next iteration:

let field;
while ((field = pbf.nextField(end))) {
    if (field === 1) obj.id = pbf.readVarint();
    else if (field === 2) obj.name = pbf.readString();
}

To read an embedded message, pass pbf.readVarint() + pbf.pos as end to a nested reader:

const msg = readSubMessage(pbf, pbf.readVarint() + pbf.pos);

Read values:

const value = pbf.readVarint();
const str = pbf.readString();
const numbers = pbf.readPackedVarint();

For lazy or partial decoding, save the position and come back to it later:

let fooPos = -1;
let field;
while ((field = pbf.nextField())) {
    if (field === 1) fooPos = pbf.pos;
}
...
pbf.pos = fooPos;
const foo = readFoo(pbf, pbf.readVarint() + pbf.pos);

A callback-based readFields(fn, obj, end) is also available for backward compatibility, but new code should prefer the nextField loop — it's significantly faster.

Scalar reading methods:

• readVarint(isSigned) (pass true if you expect negative varints)
• readSVarint()
• readFixed32()
• readFixed64()
• readSFixed32()
• readSFixed64()
• readBoolean()
• readFloat()
• readDouble()
• readString()
• readBytes()

Field iteration methods:

• nextField(end) — returns the next field number, or 0 at end-of-message; skips the previous field's value if it wasn't consumed
• skip(value) — skips a field given its raw tag varint

Packed reading methods:

• readPackedVarint(arr, isSigned) (appends read items to arr)
• readPackedSVarint(arr)
• readPackedFixed32(arr)
• readPackedFixed64(arr)
• readPackedSFixed32(arr)
• readPackedSFixed64(arr)
• readPackedBoolean(arr)
• readPackedFloat(arr)
• readPackedDouble(arr)

Writing

Create a PbfWriter (optionally with a pre-allocated Buffer or Uint8Array):

const pbf = new PbfWriter();

Write values:

pbf.writeVarint(123);
pbf.writeString("Hello world");

Write an embedded message:

pbf.writeMessage(1, writeObj, obj);

function writeObj(obj, pbf) {
    pbf.writeStringField(obj.name);
    pbf.writeVarintField(obj.version);
}

Field writing methods:

• writeVarintField(tag, val)
• writeSVarintField(tag, val)
• writeFixed32Field(tag, val)
• writeFixed64Field(tag, val)
• writeSFixed32Field(tag, val)
• writeSFixed64Field(tag, val)
• writeBooleanField(tag, val)
• writeFloatField(tag, val)
• writeDoubleField(tag, val)
• writeStringField(tag, val)
• writeBytesField(tag, buffer)

Packed field writing methods:

• writePackedVarint(tag, val)
• writePackedSVarint(tag, val)
• writePackedSFixed32(tag, val)
• writePackedSFixed64(tag, val)
• writePackedBoolean(tag, val)
• writePackedFloat(tag, val)
• writePackedDouble(tag, val)

Scalar writing methods:

• writeVarint(val)
• writeSVarint(val)
• writeSFixed32(val)
• writeSFixed64(val)
• writeBoolean(val)
• writeFloat(val)
• writeDouble(val)
• writeString(val)
• writeBytes(buffer)

Message writing methods:

• writeMessage(tag, fn[, obj])
• writeRawMessage(fn[, obj])

Misc methods:

• realloc(minBytes) - pad the underlying buffer size to accommodate the given number of bytes; note that the size increases exponentially, so it won't necessarily equal the size of data written
• finish() - make the current buffer ready for reading and return the data as a buffer slice

For an example of a real-world usage of the library, see vector-tile-js.

Proto Schema to JavaScript

If installed globally, pbf provides a binary that compiles proto files into JavaScript modules. Usage:

$ pbf <proto_path> [--no-write] [--no-read] [--legacy]

The --no-write and --no-read switches remove corresponding code in the output. The --legacy switch makes it generate a CommonJS module instead of ESM.

Pbf will generate read<Identifier> and write<Identifier> functions for every message in the schema. For nested messages, their names will be concatenated — e.g. Message inside Test will produce readTestMessage and writeTestMessage functions.

• read(pbf) - decodes an object from the given PbfReader instance.
• write(obj, pbf) - encodes an object into the given PbfWriter instance (usually empty).

The resulting code is clean and simple, so it's meant to be customized.