Zurich Toolbox for Readymade Economic Experiments

z-Tree is a widely used software package for developing and carrying out economic experiments. The language used to define the experiments is simple and compact, meaning that experiments can be developed quickly, and programming experience is not necessary, though useful.

z-Tree is flexible both with respect to the logic of interaction and the visual representation, allowing the simple programming of normal form games, extensive form games, double auctions, or clock auctions, for example. We began the development of the software in 1998, and have continually added new features.


The z-Tree software is implemented as a client-server application with a server application for the experimenter, called z-Tree, and a client application for the subjects, called z-Leaf.

The applications are programmed in C++ (Visual C++ 2015, MFC) and run on all recent released x86 32 bit and 64 bit versions of Windows, starting with Windows XP SP3.

The current version 3.6.7 has been released on June 21, 2016.

A beta release of 4.1 is available, currently version 4.0.25 (April 29, 2018).​

The most important new features are:

  • Increased performance.
  • Client side response time ("Event Time" variables).
  • Connector (allows external software to communicate with z-Leaf).
  • Variables of type boolean, color and string can be uses as a data type, also in arrays.
  • New color functions.
  • "for" loop replaces the "iterator".

We will now collect bug reports, fix then and produce a version 4.1.0 as soon as we net no bug report for at lest one week.


The program can be licensed free of charge. Please note that z-Tree may only be used for academic purposes. If you are not part of an academic institution but want to use z-Tree for research purposes, please contact us

When you report results of experiments conducted with z-Tree, the licence requires that you mention it's use in the publication and cite the article published in Experimental Economics.