Bonsai

March 8, 2026 · View on GitHub

Bonsai

An HTML minifier in pure Swift.

Zero dependencies, comprehensive test suite (149 tests ported from html-minifier-next), replicates the output of html-minifier-next with the following options:

html-minifier-next option	Notes
`caseSensitive: true`	Preserves tag and attribute name case
`collapseBooleanAttributes: true`	Also handles `draggable`, `crossorigin`, `contenteditable`
`collapseWhitespace: true`	Inline/block-aware smart collapsing
`removeComments: true`	Keeps `<!--! -->` bang comments and conditional comments
`removeEmptyAttributes: true`	`class`, `id`, `style`, `title`, `lang`, `dir`, `value`, event handlers
`removeRedundantAttributes: true`	Default values, script `language`/`charset`, `a[name]` matching `id`
`removeScriptTypeAttributes: true`	Removes `type="text/javascript"` and variants
`removeStyleLinkTypeAttributes: true`	Removes `type="text/css"` from `<style>` and `<link>`
`useShortDoctype: true`	All doctypes become `<!doctype html>`

Usage

Include Bonsai in your Package.swift:

let package = Package(
  dependencies: [
    .package(url: "https://github.com/loopwerk/Bonsai", from: "1.0.0"),
  ],
  targets: [
    .target(
      name: "MyProject",
      dependencies: ["Bonsai"]),
  ]
)

Using it is a simple import and function call:

import Bonsai

let result = Bonsai.minifyHTML("<html>")

There are no options or settings to configure.

Performance

Benchmarked on a ~143 KB HTML page (1000 iterations, release build), using a M1 Max Macbook Pro:

Tool	Avg time per operation	Throughput
html-minifier (Node.js)	12.1 ms	83 ops/sec
html-minifier-terser (Node.js)	14.3 ms	70 ops/sec
html-minifier-next (Node.js)	0.6 ms	1,817 ops/sec
Bonsai (Swift)	0.9 ms	1,149 ops/sec

The speed difference between Bonsai and html-minifier-next only becomes noticeable at scale; for individual pages, both finish under a millisecond.

To run the benchmark yourself:

# Swift (release mode)
swift run -c release BonsaiBenchmark