z-Tree unleashed enables you to run your z-Tree experiments over the Internet. Subjects can participate from anywhere in the world.

z-Tree unleashed is permissively licensed under a MPL-2.0-style license. The only additional requirement is that you cite the following paper if you use z-Tree unleashed in an academic context:

Duch, M. L., Grossmann, M. R. P. and Lauer, T. (2020). “z-Tree unleashed: A novel client-integrating architecture for conducting z-Tree experiments over the Internet”. Working Paper Series in Economics No. 99, University of Cologne.

DOI: 10.13140/RG.2.2.11801.36961

Please read our working paper! It’s sorta awesome.

z-Tree unleashed is a set of scripts that should run on most POSIX compatible x86 or x64 platforms.

Our suggested method of installing z-Tree unleashed:

Via our virtual machine image: You can simply download our virtual machine image and import it into VirtualBox. After some simple steps, you’re all set.
Proceed to the section entitled “Installation”.


Show Highlights

- Use just one computer to host up to 95 z-Leafs over the internet.

- Participants just need a webbrowser. No additional software is required.

- We use antialiasing to improve the display appearance of z-Tree unleashed.

(This feature is default in a Windows lab environment, and now your Experiment looks the same over the internet using z-Tree unleashed.)

- You may use it in a stationary lab.

The advantages are:
  • You don't need a shared fileserver anymore.
  • You don't need to update all computers with a new Version of z-Tree.
  • You may use client names matching your cabin numbers.
  • It just requires VirtualBox to be installed and a Bridged Adapter to be set up