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Running experiments online


About OSWeb

OSWeb is an online runtime for OpenSesame experiments. That is, it is a JavaScript library that interprets and executes OpenSesame experiments.

The OSWeb extension

The OSWeb extension for OpenSesame (Figure 1) allows you to test experiments in a browser, and to export experiments in a format that you can import into JATOS (desribed below).

The extension is pre-installed in the Windows and Mac OS packages of OpenSesame 3.2.6 and later.

Alternatively, you can install the extension manually. It is available on PyPi as opensesame-extension-osweb and can be installed as described here:


Figure 1. The OSWeb extension for OpenSesame.

Testing the experiment in a browser

  • In OpenSesame, open the OSWeb extension (Menu → Tools → OSWeb).
  • The extension will perform a simple (and incomplete) check to see if your experiment appears to be compatible with OSWeb.
  • If no problems are detected, click 'Test experiment in external browser'.
  • This will open the experiment in your default browser so that you can check if the experiment runs as expected (Figure 2).


Figure 2. The welcome screen of OSWeb when testing the experiment in a browser.

Supported functionality

The following items are supported by OSWeb:

  • advanced_delay
  • feedback (named elements not supported)
  • keyboard (key release not supported)
  • logger
  • loop
  • mouse (mouse release not supported; linked sketchpad not supported)
  • notepad (does nothing)
  • repeat_cycle
  • reset_feedback
  • sampler
  • sequence
  • sketchpad (named elements not supported)
  • synth
  • touch_response


Currently, you need to host your own JATOS installation to manage experiments.


JATOS is a system for managing online experiments. It allows you to create accounts for experimenters, upload experiments, and generate links that you can distribute to participants. JATOS needs to be installed on your own web server. However, for testing purposes, you can use the JATOS test server (Figure 3).

Exporting your experiment to a JATOS study

  • In OpenSesame, open the OSWeb extension (Menu → Tools → OSWeb)
  • Click on 'Export experiment as JATOS study'
  • Save your experiment as a .zip file

Importing your experiment in JATOS

  • In JATOS, click on 'Import study' (Figure 4)
  • Select the .zip file that you have exported from OpenSesame
  • Once the file has been uploaded to the server, JATOS will ask you to confirm that you want to import the study
  • Click on 'Import' to confirm
  • The study now appears in the list of studies on the left-hand side (Figure 5)


Figure 3. For testing purposes, you can use the JATOS test server.


Figure 4. Click on 'Import study' and select the .zip file that you have exported with the OSWeb extension.


Figure 5. Once the experiment has been successfully imported in JATOS, it appears in the list of experiments.

Example experiments

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