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🌱 Fresh environment

A Fresh environment is a fast and ready-to-use Docker container with various developer tools pre-installed. Including Node.js, and headless browsers. It aims to help to run npm packages on your machine, without putting your personal data at risk!

Quick start

Run the install command from the terminal:

curl -fsS '' | base64 --decode | python3

This will download fresh-node, verify its integrity, and save it to /usr/local/bin/ or $HOME/.local/bin. Programs in these directories automatically become available as commands on your terminal.

Review fresh-install source.

What's inside

  • Node.js with npm
  • Firefox
  • Chromium
  • chromedriver, ffmpeg, and xvfb (for browser tests)
  • JSDuck
  • Debian Linux


You'll need to have Docker installed. See Docker CE for Linux, Docker for Mac, or Docker for Windows.

On Linux, Podman can also be used.

Issue tracker

Report bugs or feature requests to Wikimedia Phabricator.


With Fresh installed, navigate your terminal to a project directory in which you might need to run commands like npm install or npm test. Before you run such commands, use fresh-node to enter a Fresh environment.

you@precious.local:~$ cd myproject/
you@precious.local:myproject$ fresh-node

# 🌱 Fresh! ░ Node.js … ░ npm … ░ Firefox … ░ Chromium … ░ Debian …
# mount: /myproject ➟ /Users/you/myproject (read-write)


You can now execute commands such as npm install, npm test, and other npm run commands.

It is recommended to keep Fresh environments open for a given project, so that subsequent commands can benefit from npm caching, tab completion, and to reduce chances of accidentally running commands on your host machine instead.

To run a single command without launching a shell, use fresh-node -- <command>, e.g. fresh-node -- npm install.

How does it work

The first time you start a Fresh environment, Docker will download the container image layers from This may take a few minutes.

The fresh-node command uses the node-test-browser image from Jenkins CI at Wikimedia Foundation. This means you can trust that if it works in Fresh, it'll work in CI. And vice-versa, you can use Fresh to locally reproduce test failures.


Fresh is fast. Creating and launching a new container takes only a fraction of a second. This is made possible by Docker and its docker run command. It doesn't need to copy or clone anything. Instead, it references the downloaded Docker image as bottom layer (read-only) in an empty container, with a new (initially empty) read-write layer on top. This uses the "copy-on-write" principle, powered by UnionFS.


You can start as many independent Fresh environments as you want, without taking up a lot of disk space, and without different sessions affecting each other.

Only the directory from which you launch Fresh, is made visible to the container. The rest of your personal hard drive is not mounted, and most networking capabilities are also disabled (except toward the Internet). Specifically, local servers and networked devices on your home network are not easily reachable.

Any changes made elsewhere in the container, are lost once you exit Fresh.


When you open an application or execute a program from the terminal, that program can do anything that you can do. This should scare you.

See also The worst that could happen.

To create your own Docker base image, see