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The latest stable version is 4.0 Melodramatic Milgram (release notes).


The Windows package is based on Python 3.11 for 64 bit systems. The installer and .zip packages are identical, except for the installation. Most people download the installer package (green button).

Standard Windows installer (.exe)

Standard Windows no installation required (.zip)

Mac OS

This article on the Mac OS support site explains how to override the security settings of Mac OS that will by default prevent OpenSesame from launching. The first time that you start OpenSesame it will take a very long time before the application starts; subsequent launches go much faster.

The package below is built for Intel processors but also runs on ARM (M1) processors.

Python 3 for Intel x64 Mac OS package (.dmg)

To install OpenSesame with Homebrew, run the following command in a terminal:

brew install --cask opensesame


Packages are developed and tested on Ubuntu 22.04 Jammy Jellyfish. Packages are only available for 22.04 and 22.10.

If you have OpenSesame 3.X installed, first deinstall all packages . This is required to avoid package conflicts due to slight renaming of some packages in OpenSesame 4.0.

# If necessary: uninstall OpenSesame 3.X
sudo apt remove python3-opensesame python3-pyqode.python python3-pyqode.core python3-rapunzel python3-opensesame-extension* python3-opensesame-plugin*

Next, to add the required repositories to your software sources and install OpenSesame (and Rapunzel), run the following commands in a terminal:

# Add repository for stable packages
sudo add-apt-repository ppa:smathot/cogscinl
# Add repository for development packages
sudo add-apt-repository ppa:smathot/milgram
# Install OpenSesame 4.X packages plus useful extensions
sudo apt install python3-opensesame python3-rapunzel python3-opensesame-extension-updater python3-pygaze python3-pygame python3-opensesame-extension-language-server

Some commonly used packages are not available through the PPA. You can install them through pip:

# Install optional packages that are only available through pip
pip install --pre opensesame-extension-osweb opensesame-plugin-psychopy opensesame-plugin-media_player_mpy

PsychoPy is best installed through pip, because the Ubuntu package is currently broken.

# Install psychopy
pip install psychopy psychopy_sounddevice python-bidi arabic_reshaper

PyPi (crossplatform)

All packages can be pip-installed. Note that OpenSesame is called opensesame-core on PyPi.

pip install --pre opensesame-core rapunzel opensesame-extension-osweb opensesame-extension-updater opensesame-plugin-psychopy opensesame-plugin-media_player_mpy
pip install psychopy psychopy_sounddevice pygame

Once you have installed all packages, you can simply run OpenSesame by (after having activated the correct environment) running:


Or for the Rapunzel code editor:


Anaconda (cross-platform)

First, create a new Python environment for OpenSesame (optional):

conda create -n opensesame-py3
conda activate opensesame-py3

Next, add the relevant channels (cogsci) and (conda-forge) and install all relevant packages. Make sure that pyqode.core and pyqode.python are >= 3.2 from the cogsci channel, and not the older versions from the conda-forge channel.

conda config --add channels conda-forge --add channels cogsci
conda install opensesame opensesame-extension-osweb opensesame-extension-updater opensesame-plugin-psychopy rapunzel pygaze qtconsole pyqtwebengine wxpython

Some packages are not available through conda. You can use pip install for these. (PsychoPy is known to fail to install on some systems, which is why it is installed separately below.)

pip install soundfile pygame
pip install psychopy psychopy-sounddevice

Once you have installed all packages, you can simply run OpenSesame by (after having activated the correct environment) running:


Or for the Rapunzel code editor:


Older versions

Older versions can be downloaded from GitHub releases:

Source code

The source code of OpenSesame is available on GitHub.


Which version of Python to use?

OpenSesame is currently built and tested with Python 3.11 Others versions of Python >=3.7 work but are not extensively tested. Python 2 is no longer supported. The last release that included a Python 2 package was 3.3.12, which can still be downloaded from the release archive.

When (not) to update?

  • Update while developing and testing your experiment; it is always best to use the latest version of OpenSesame.
  • Do not update while running an experiment; that is, do not update while you are collecting data.
  • Run an experiment with the same version of OpenSesame that you used for developing and testing.

Manually upgrading packages

OpenSesame is a regular Python environment, and you can upgrade packages with pip or conda as described here:

Tips for system administrators

  • When a new major version of OpenSesame is released (with a version ending in 0, e.g. 3.1.0), it is generally followed quickly by one or two maintenance releases (e.g. 3.1.1 and 3.1.2) that address major bugs. Therefore, if you are installing OpenSesame on systems that you do not update often, it is best to wait until the second or third maintenance release (e.g. 3.0.2, 3.1.3, etc.). That way you minimize the risk of rolling out a version of OpenSesame that contains major bugs.
  • The Windows installer allows you to silently install OpenSesame using the /S flag.
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