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LIONESS Lab is a free web-based platform for online interactive experiments. LIONESS experiments include standardized methods to deal with group formation, handling participant dropout and other challenges of online interactive experiments.

With LIONESS Lab you can readily develop and test your LIONESS experiments online in an user-friendly environment. You can develop experiments from scratch in a point-and-click fashion or start from an existent design from our growing repository and adjust it according your own requirements. A what-you-see-is-what-you-get interface allows you to easily define participant screens. You can use JavaScript for any programming - e.g. to calculate payoffs or manipulate variables. You can use a range of ready-made functions to get data from (and write to) the server.

Once your LIONESS experiment is ready, you can download it and run it on your own server. Participants can then be invited to online sessions, e.g. by using Amazon Mechanical Turk (MTurk). At the end of a session, you can download a spreadsheet with the data, as well as a file to automate bonus payments on MTurk. Using LIONESS Lab you can choose to share LIONESS experiments with your co-authors and other experimenters.

LIONESS experiment

LIONESS experiments include standardized methods to deal with group formation, participant dropout and other challenges of online interactive experiments. Learn more about all methods here and how to use the Control panel.


LIONESS Lab runs as a online tool on a central webserver. No installation is needed. Just register for an account and get started.


Develop your LIONESS experiments screen-by-screen. LIONESS Lab offers a wide range of elements for inputs, texts and programs. You can also copy existing experiments from the repository and modify them according to your needs.


After developing, you can directly test the experiment in LIONESS Lab. You can invite co-authors to have a look at the instructions and test the experiment as well and directly implement their suggestions into your experiment.


To run a session you can download your experiment and upload it to your own server. Participants can enter your LIONESS experiment through a link (posted on, e.g., a crowd-sourcing website). The progress of a session can be monitored through the control panel.


You can choose to share your experiments with other researchers via LIONESS Lab or get access to experiments of others via the growing repository of experiments. Every shared experiment can be replicated and adjusted by experimenters.

Further details

Terms of Use


Please notice that LIONESS Lab is still a beta version. It comes with ABSOLUTELY NO WARRANTY.

We are constantly improving our platform. Experimenters using our platform, as well as ourselves continuously contribute new designs to the repository. Moreover, the basic functionality of the builder tool is continuously being updated.


If you have any questions, support issues or would like to report a bug, please contact us at


The basic LIONESS logic was developed by Lucas Molleman, Antonio A. Aréchar and Simon Gächter at the Centre for Decision Research and Experimental Economics (CeDEx) at the University of Nottingham, with support from the European Research Council (ERC-AdG 295707). LIONESS Lab is powered by classEx, developed by Marcus Giamattei and Johan Graf Lambsdorff at the University of Passau.