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JATOS (Just Another Tool for Online Studies) is free, open-source software that lets researchers host and run browser-based studies on a server they control. It is not a statistic or an analysis method: it is the server layer that sits between the experiment you build and the participants who take it. This guide is for researchers (mostly in psychology and cognitive science) who want to know what JATOS does, what it works with, where it can run, and how to cite it.
What JATOS is
JATOS describes itself as a tool that helps you set up and run online studies directly on your own server, which gives you control over your research data and supports compliance with ethical guidelines (jatos.org, read 2026-11-08). It is released under the Apache License 2.0 and is free to use. It has a graphical interface, so managing the server does not require terminal commands.
The software was introduced in a 2015 paper by Lange, Kuhn and Filevich in PLOS ONE, which describes it as an open-source, cross-platform web application with a graphical interface that simplifies setting up and communicating with a web server hosting online studies written in JavaScript. That paper reports installation on Windows, Mac OS X and Linux, pairing with a database for secure data storage, and the option to install locally to test feasibility before setting up a server. It describes the 2015 release, so check the current documentation for today’s features.
How JATOS works: from study to results
Following the project’s own description, the workflow has four parts:
- Build the study with a browser-based experiment tool, or with your own JavaScript, HTML and CSS.
- Host it in JATOS on a server you administer (for example a university server or a cloud server).
- Recruit participants through a platform such as Prolific or MTurk, or by other means, and send them to the study link.
- Collect results on your own JATOS instance rather than on a third-party experiment service.
What JATOS works with
The JATOS homepage lists these study builders as compatible: OpenSesame, jsPsych and lab.js, plus studies written directly in JavaScript, HTML and CSS. Its documentation also covers PsyToolkit and PsychoPy. For recruitment it names Prolific and MTurk and says other routes work too. On the CASRAI side, see Prolific vs MTurk for participant recruitment and the Prolific guide.
Hosting options
| Option | What the JATOS sources say |
|---|---|
| Your own server | Install on a server you control, such as a university server or a cloud server. This is the setup JATOS is designed around. |
| Local installation | The 2015 paper describes installing locally to test feasibility before setting up a server. |
| Demo server | The site offers a “Try Out” demo server for trying the interface. |
| MindProbe | A free JATOS instance sponsored by the European Society for Cognitive Psychology (ESCoP), whose official journal is the Journal of Cognition. |
Data, privacy and ethics
Running your own instance means the study data are stored where you decide, which is the project’s stated route to control over research data. The JATOS documentation has a dedicated “Data privacy and ethics” section; read it alongside your institution’s review requirements. JATOS does not replace ethics approval or consent: you still need a protocol and a proper consent process for online participants. See informed consent in research and the informed consent definition.
Is JATOS open source?
Yes. It is licensed under Apache License 2.0. For what that means in practice, see open source software and open source licenses.
How to cite JATOS
The JATOS project points to the 2015 paper as its citation. APA 7th-style reference:
Lange, K., Kuhn, S., & Filevich, E. (2015). “Just another tool for online studies” (JATOS): An easy solution for setup and management of web servers supporting online studies. PLOS ONE, 10(6), e0130834. https://doi.org/10.1371/journal.pone.0130834
Also report the JATOS version you ran and the builder tool and its version, so others can reproduce your setup.
FAQ
What does JATOS stand for?
Just Another Tool for Online Studies.
Is JATOS a statistical test?
No. It is server software for hosting and running online studies and storing their data. Statistical analysis happens afterwards in whatever software you use for analysis.
Do I need to write code or use the command line?
Managing the JATOS server is done through a graphical interface. The study itself is built in a tool such as jsPsych, lab.js or OpenSesame, or written in JavaScript, HTML and CSS.
Does JATOS recruit participants?
No. You recruit through a platform such as Prolific or MTurk, or another route, and direct participants to your JATOS-hosted study.
Can I try it without setting up a server?
The JATOS site offers a “Try Out” demo server, and the 2015 paper describes a local installation for testing.
Sources
- JATOS project site, https://www.jatos.org/ and https://www.jatos.org/Whats-JATOS.html (read 2026-11-08).
- Lange, K., Kuhn, S., & Filevich, E. (2015). PLOS ONE, 10(6), e0130834. https://doi.org/10.1371/journal.pone.0130834 (PubMed 26114751, read 2026-11-08).
