Web Bundles

This is a Node.js module for serializing and parsing the application/webbundle format defined in the Web Bundles draft spec.

Installation

Using npm:

npm install wbn

Usage

Please be aware that the API is not yet stable and is subject to change any time.

Creating a Bundle:

import * as fs from 'fs';
import * as wbn from 'wbn';

const builder = new wbn.BundleBuilder();
builder.addExchange(
  'https://example.com/', // URL
  200, // response code
  { 'Content-Type': 'text/html' }, // response headers
  'Hello, Web Bundle!' // response body (string or Uint8Array)
);
builder.setPrimaryURL('https://example.com/'); // entry point URL

fs.writeFileSync('out.wbn', builder.createBundle());

Reading a Bundle:

import * as fs from 'fs';
import * as wbn from 'wbn';

const buf = fs.readFileSync('out.wbn');
const bundle = new wbn.Bundle(buf);
const exchanges = [];
for (const url of bundle.urls) {
  const resp = bundle.getResponse(url);
  exchanges.push({
    url,
    status: resp.status,
    headers: resp.headers,
    body: new TextDecoder('utf-8').decode(resp.body),
  });
}
console.log(
  JSON.stringify(
    {
      version: bundle.version, // format version
      exchanges,
    },
    null,
    2
  )
);

CLI

This package also includes wbn command which lets you build a web bundle from a local directory. For example, if you have all the necessary files for https://example.com/ in static/ directory, run the following command:

$ wbn --dir static \
      --baseURL https://example.com/ \
      --output out.wbn

Run wbn --help for full options.

Note: currently this CLI only covers a subset of the functionality offered by gen-bundle Go tool.

Backwards compatibility

This module supports creating and parsing Web Bundles that follow different draft versions of the format specification. In particular:

• version b2 follows the latest version of the Web Bundles spec (default)
• version b1 follows the previous version of the Web Bundles spec

To create a new bundle with the b1 format, pass the version value to the constructor:

const builder = (new wbn.BundleBuilder('b1'))
  .setPrimaryURL('https://example.com/')
  .setManifestURL('https://example.com/manifest.json')
  .addExchange(...);

fs.writeFileSync('out_b1.wbn', builder.createBundle());

Likewise, the wbn command can optionally take a --formatVersion b1 parameter when creating a new Web Bundle.

This module also takes care of selecting the right format version automatically when reading a bundle. Check the property bundle.version to know the decoded bundle's format version.

Using Bundles

Generated bundles can be opened with web browsers supporting web bundles.

Chrome (79+) experimentally supports navigation to Web Bundles with some limitations. See this document for more details.

Chrome (104+) supports [`