ASTX — Abstract Syntax Tree Executable

ASTX is an AST-based binary format for JavaScript. Instead of distributing raw source code, you compile JavaScript to a compact binary that any JavaScript runtime can execute via the ASTX runtime library.

Status: Early stage – APIs may change between releases.

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Why ASTX?

Goal	How ASTX achieves it
Smaller distribution size	AST nodes are encoded with MessagePack and compressed with Zstd (level 22)
AOT optimisations	The compiler runs a configurable pipeline of AST transformers before encoding
Obfuscation	Binary format is significantly harder to reverse-engineer than minified JS
Runtime independence	The runtime only needs a JS engine – Node.js, Deno, Bun, or a browser
Full JS feature support	Works at the AST level, so any syntactically valid JS can be compiled

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Packages

Package	Description
@astx/compiler	Parses, optimises, and encodes JS → .astx
@astx/runtime	Decodes and executes .astx files
@astx/shared	Shared types, constants, and the wire-format spec
@astx/cli	Command-line interface (astx compile / run / gen)

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Quick start

Install

# Compiler (e.g. in a build script)
npm install @astx/compiler

# Runtime (e.g. in your app)
npm install @astx/runtime

# CLI (global)
npm install -g @astx/cli

Compile

import { compile, saveToFile } from "@astx/compiler";

const program = compile(`
  function greet(name) {
    console.log("Hello, " + name);
  }
  greet("world");
`);

await saveToFile(program, "greet.astx");

Run

import { loadFromFile, run } from "@astx/runtime";

const program = await loadFromFile("greet.astx");
run(program, { mode: "vm" });

CLI

astx compile src/index.js dist/index.astx
astx run dist/index.astx

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Binary format (v0x02)

[MAGIC_HEADER: 4 bytes] [FORMAT_VERSION: 1 byte] [Zstd-compressed payload]
                                                         │
                               ┌─────────────────────────┘
                               ▼  (MessagePack array)
                        [valueDict, bytecode, sourceMap | null]

• valueDict – deduplicated string/number/other literal values
• bytecode – deduplicated array of encoded AST node arrays (index-referenced)
• sourceMap – optional [line, col][] per bytecode slot; null entries for synthetic nodes

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Monorepo setup

This repo is managed with pnpm workspaces and Turborepo.

# Install dependencies
pnpm install

# Build all packages
pnpm -r build

# Type-check all packages
pnpm -r check-types

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License

GPL-3.0 — see individual package LICENSE files for details.