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JATOS (Just Another Tool for Online Studies) is a platform that allows researchers to manage, distribute and run studies online using their own servers. Participants can access these studies via the internet on any device with a browser; and researchers can login to JATOS to upload, customize and manage studies, and export their data.

Study components can be built manually with HTML, CSS and JavaScript; or using third-party packages, such as OpenSesame, lab.js, or jsPsych. JATOS can also be interfaced with Prolific, SONA and Qualtrics.

SOLO makes a JATOS instance available at no cost to researchers, and can offer limited technical support in building and running JATOS studies, as well as post-processing the data it generates. For more information, see SOLO JATOS server.

Building Studies for JATOS

JATOS supports experiments built with a variety of tools, the most notable of which are listed in this section. Note that these are all free software. For most users and most use-cases, SOLO recommends using OpenSesame or jsPsych. Fully custom studies can also be built using HTML, CSS and JavaScript, together with their thousands of freely available libraries. Python cannot be used for scripting in this context.

OpenSesame & OSWeb

OpenSesame is a free and open-source program for developing interactive experiments, and is already in use by various researchers at the FSW. Its latest version includes the OSWeb plug-in, which allows its experiments to be exported for use with JATOS—albeit with some important caveats. OSWeb does not support all OpenSesame features, and the customary Python-based in-line scripts must be replaced with their JavaScript-based counterparts. Please see the OSWeb documentation for more information.

The full OpenSesame to JATOS workflow is explained in great detail in this YouTube playlist. Additionally, the OpenSesame website features a very active forum where enquiries about OSWeb and OpenSesame itself can be posted and browsed through.


According to the lab.js website:

“lab.js is a free, open, online study builder for the behavioral and cognitive sciences. (it works great in the lab, too)”.

lab.js is essentially a JavaScript library that can be used to create experiments, either via coding, or using its very easy-to-use online experiment builder. The builder, as well as the library itself, features good documentation, and the ability to very easily export your experiments for JATOS, as described here.


According to the jsPsych website:

“jsPsych is a JavaScript library for running behavioral experiments in a web browser. The library provides a flexible framework for building a wide range of laboratory-like experiments that can be run online.”

Unlike lab.js, jsPsych is purely a JavaScript library and does not features a graphical experiment builder interface. As such, it may be more difficult for people with limited programming experience. Nevertheless, it is a very powerful and flexible tool for coding JATOS-compatible experiments, and includes a sizable collections of useful plug-ins.

Additional Interfaces

JATOS can be configured to automatically receive information about participants, sessions, groups etc. before a study begins, or to pass study information and results on to another site after the study has finished. This generally occurs using Query Strings that conforms to the other applications specifications. This allows, for instance, that students are automatically assigned SONA credits after successfully completing a study.

For technical support regarding the platforms listed below, information about their interfacing features, and the extent to which your institute has access to them, please contact their respective support units: