Last modified by Iris Spruit on 2023/08/04 13:19


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 OSWeb, lab.js, or jsPsych. JATOS can also be interfaced with ProlificSONA and Qualtrics.

SOLO makes a JATOS server available at no cost to FSW researchers.

Support and Advice

SOLO can offer technical support in building and running JATOS studies, as well as post-processing the data it generates. For researchers with limited programming experience, SOLO recommends building JATOS compatible tasks in OpenSesame/OSWeb. However, for researchers with JavaScript experience seeking to build complicated tasks, jsPsych provides a much more flexible solution.

If you have any questions regarding JATOS, please email labsupport@fsw.leidenuniv.nl.


The SOLO JATOS server is available at no cost to FSW researchers (and for now to all Leiden University researchers in general), and can be reached via: jatos.services.universiteitleiden.nl

The JATOS GUI can only be accessed from inside the Leiden University intranet, see below.

Requesting Access

All students and staff of Leiden University can request an account. To request a user account, please send an email to labsupport@fsw.leidenuniv.nl and include the following information:

  • Name and description of the study, or studies, to be conducted on JATOS.
  • For each user requiring access, include their full name, ULCN account and university email.
  • Please indicate the estimated start and end-date of required JATOS access.

JATOS Usage Guidelines

When using the SOLO JATOS server, the following rules must be observed:

  • If the JATOS account is not tied to a ULCN account, please change the JATOS password immediately upon reception.
  • JATOS accounts are strictly personal.
  • Please indicate if an account is no longer active and can be removed.

Password Reset

If you lost your JATOS password, you can request that it be reset by contacting labsupport@fsw.leidenuniv.nl.

Accessing the JATOS GUI

For security reasons, the JATOS GUI can only be accessed from within the Leiden University intranet. Studies, however, can be run by anyone with access to the internet. Attempting to navigate to jatos.services.universiteitleiden.nl from outside the university network will result in a 403 Bad Gateway error.

To access the JATOS GUI, navigate to the server using:

  • a browser on any ISSC-issued PC or laptop connected to the university network.
  • a virtual browser in the Remote Workplace (Citrix).
  • a browser on your own university PC, accessed via Remote Desktop Protocol (RDP).
  • a browser on any PC connected to EduVPN.

University PC

Any desktop or laptop connected to a wired or wireless Leiden University network should be able to reach the JATOS GUI (jatos.services.universiteitleiden.nl). Eduroam, however, does not provide access to the JATOS GUI.


The JATOS GUI can be accessed through a virtual browser in Citrix by going to remote.campus.leidenuniv.nl, opening the "Google Chrome via Citrix" application. Note that running a study in the Citrix browser has been observed not to work correctly. Instead, only use the Citrix browser to manage the study, and run it in your native browser. This can be done by generating a General Multiple Worker, copying the link and opening the link in a native browser on your PC. If you are using the lightweight Citrix application (inside your native browser), you can copy to your device by clicking the Citrix icon (top center) and going to the Clipboard.


University staff can remotely gain control of their own personal work PCs using the Remote Desktop Protocol (RDP). Through RDP, the JATOS GUI can be accessed normally. For more information about RDP, please visit refer to the ISSC Helpdesk. Note that the RDP service is subject to approval by the ISSC and may not be available to everyone.


The JATOS GUI is accessible from a PC connected to EduVPN (with the Leiden University profile).


If you cannot access the JATOS GUI, double-check the following:

  • If you are getting a 403 Bad Gateway error, you are not on the university network. See above.
  • Make sure you are navigating to the secure site (include the https://): https://jatos.services.universiteitleiden.nl. If the https:// is omitted on the first visit, your browser will not find the site. This is due to the HSTS setting of the server. This also holds when accessing studies; as such, it is vitally important to include the https:// part when distributing JATOS links.

GDPR and Data Security

All studies conducted using the JATOS server must comply with the relevant regulations and guidelines; including, but not limited to, those regarding GDPR, Informed Consent, etc. In addition, all studies must be officially approved by the concerning authorities—ethical, medical and/or otherwise—before going public. Questions regarding these matters can be sent to privacy@fsw.leidenuniv.nl.

The JATOS server is maintained by the ISSC, and is physically located in The Netherlands. The data are backed-up regularly in an encrypted fashion, and all data are stored in compliance with the security regulations of Leiden University. Both participants and users communicate with the JATOS server exclusively through a secure internet connection (https).

Within JATOS, users only have access to studies that they have explicitly been made are members of. After a study has finished, and SOLO has confirmed that the data have been downloaded and secured, the study and all its data will be removed from the server. Accounts of users that are then no longer members of any other studies will also be removed.

SOLO and the ISSC will perform updates and/or maintenance to JATOS and/or its dependencies when they see fit, especially with regards to security patches. Users will be informed beforehand about possible downtime, and about expected consequences for ongoing studies.

Typical OpenSesame/OSWeb Workflow

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.

The following is a standard workflow for developing and deploying a study on the SOLO JATOS server:

  1. Contact SOLO Lab-support:
    • It is recommended that you contact SOLO lab-support (labsupport@fsw.leidenuniv.nl) as soon as possible to announce your intention to use the JATOS server and describe your plans. This way, lab-support can provide you with relevant advice and access to the server.
  2. Build OpenSesame experiment:
    • Familiarize yourself with OpenSesame and its OSWeb-plugin. Then build your experiment and test it out in your own browser using the OSWeb test feature.
  3. Test experiment on local JATOS server:
    • Download and install a local JATOS test server, as described here. Read all relevant JATOS documentation, export the OpenSesame experiment for use in JATOS and upload it to your local JATOS server. Test the experiment thoroughly, and pay extra attention to the integrity of the data-saving process and the manner in which you wish to distribute your study once public. Once all functionality has been validated, export your study from the local JATOS server.
  4. Upload the experiment to the SOLO JATOS server:
    • Upload the study you exported from your local JATOS server to the SOLO JATOS server using the account you received from lab-support.
  5. Run the study:
    • Once the study is online, double-check everything, and distribute it when ready.
  6. Finishing up:
    • Once data collection has been completed, and the data downloaded and secured, remove the study from the server. When user accounts are no longer needed, please delete them.

Linking To and From Jatos

Worker Links

To link to Jatos experiments, you first need to make Worker links. There are multiple types of links possible, usually the most convenient is the general multiple worker. Please see these two pages for more info:

To redirect from Jatos to a different website (e.g. SONA or Qualtrics), you can use the redirect feature:

Query Parameters

You can use query parameters both in the link to Jatos (e.g. from SONA) and in the redirect from Jatos, e.g. to pass on participant id.


AccountsWho can get accounts on JATOSFor now, we will accept all account requests from students and staff of Leiden University.

JATOS Showcase

Examples showing the various JATOS features (taken from the JATOS site):


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