Overview

ES Runtime is a secure, standards-based JavaScript runtime for the server, built on V8 in Rust. It runs standard ES Modules with a sandboxed module system.

Info

Ships in two shapes from one core: an embeddable library, which is deny-by-default, and the standalone CLI (esrun), which grants all capabilities.

It is not Node.js-compatible — see Scope & non-goals and the runtime comparison.

Principles

ESM only. There is no CommonJS interop. Modules are real ES Modules and packages must expose an ESM entry point.
Capabilities are explicit. Host powers — environment, filesystem, network — are granted one at a time. Nothing is ambient.
Standard surface. Host functionality is exposed through runtime: module imports rather than magic globals.

Install

Download a prebuilt, checksum-verified binary for your platform:

shTerminal

curl -fsSL https://raw.githubusercontent.com/Open-Tech-Foundation/ES-Runtime/main/install.sh | bash

powershellPowerShell

irm https://raw.githubusercontent.com/Open-Tech-Foundation/ES-Runtime/main/install.ps1 | iex

Prefer to build from source? See the README.

Run a script

Shell

# Run a module file
esrun app.js

# Evaluate an inline snippet (top-level await is supported)
esrun -e='console.log(await Promise.resolve(42))'

# Pass arguments through to the script
esrun app.js --name Ada

Two rules cover every flag:


`--flag` or `--flag=value`	A value is never a separate word — `--timeout=500`, not `--timeout 500`
esrun's flags come first	Everything after the script belongs to the script

Both are enforced, not conventions: a value arriving as a separate word would be indistinguishable from the script path, and a flag written after the script would silently do nothing. Details: esrun CLI.