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runtime.js is an open-source library operating system (unikernel) for the cloud that runs JavaScript, can be bundled up with an application and deployed as a lightweight and immutable VM image.

It's built on V8 JavaScript engine and uses event-driven and non-blocking I/O model inspired by Node.js. At the moment KVM is the only supported hypervisor.

It tries to be compatible with npm module ecosystem and supports some of the Node.js API.

WARNING: project is in development and not ready for production use.


First thing is the command line tool runtime-cli, it will add runtime command to the shell. Type runtime to get full usage help.

npm install runtime-cli -g

Make sure QEMU is installed, it enables running applications locally.

brew install qemu           # OSX
sudo apt-get install qemu   # Ubuntu

Getting Started

Create new project and add index.js entry point file:

mkdir project
cd project
npm init
npm install runtimejs --save
echo "console.log('ok')" > index.js

Run project locally in QEMU:

runtime start

That's it, it should start and print ok in the console.

Optionally you can let it watch directory for changes and restart QEMU automatically:

runtime watch

How does it work?

There are two main components: operating system kernel and a JavaScript library.

The kernel is written in C++ and manages low-level resources like CPU and memory, runs JavaScript using embedded V8 engine. Library drives the entire system and manages hardware devices (usually virtualized by hypervisor).


API docs


Modules and projects developed by the community for runtime.js


Apache License, Version 2.0