We have an experimental econ lab with client machines for each experimental subject and a server machine. Does otree need to be install on all the client machines or just the server?

An overview of the environment used by otree would be helpful.  Is there documentation for this?

All experiments programmed in oTree are run browser-based.

(Interestingly, this isn’t mentioned anywhere on https://www.otree.org.)

You can have a look at the example games over at https://otree-more-demos.herokuapp.com/demo.

So, no, you don’t have to install oTree on the clients. (You *can* install it on each computer individually if necessary – say, for extremely computationally demanding experiments – but for most studies that is not the case.)

All you need on the clients is a (modern) browser, plus a network connection so they can request data via HTTP from the server.

For local installation, see https://otree.readthedocs.io/en/latest/install-nostudio.html and https://otree.readthedocs.io/en/latest/server/intro.html.