oTree Architecture

What is oTree?

  • oTree is a platform/software package to run online/lab experiments.

  • Participants interact with the experiments and with each other by using their browsers

  • oTree runs on/as web server

    • It may run on your computer for development (local installation)

    • It runs on a physical server (Server setup)

    • It runs on cloud services (Heroku, oTree hub, AWS, DigitalOcean etc.)

  • It has two modes:

    • Manual programming (Dominantly Python)

    • Point-and-click interface (oTree Studio)

  • In this book we teach and refer to the the first mode.

  • Point-and-click interface is available here: oTree Studio (Free for small/medium sized projects, paid subsription of the rest)

oTree and z-Tree comparision

This comparision is for those who already use z-Tree [1]. If you don’t know what z-Tree is or you have never used it, please feel free to skip.

z-Tree is click & run, oTree needs a server


Fig. 1 z-Tree: Click and Run


Fig. 2 oTree: Server

If you use z-Tree, you know that, for a basic setup, all you need to do is to run ztree.exe on your server machine and zleaf.exe on your clients with few clicks and that’s it. oTree is a little complicated than that. It should be running on a server.

z-Tree needs client software, oTree doesn’t.

  • With z-Tree, clients require a software to run on their computer. With oTree they connect to the experiment with a web browser (Firefox, Chromium, Google Chrome etc.).


Urs Fischbacher. Z-tree: zurich toolbox for ready-made economic experiments. Experimental economics, 10(2):171–178, 2007.