OpenSesame videos
Python videos
Supported by Supported by


What would you like to do?


All download options

The latest stable version is 3.3.9 Lentiform Loewenfeld, released on April 10, 2021 (release notes).


The standard download is based on Python 3.7 for 64 bit systems. The installer and .zip packages are identical, except for the installation.

Standard Windows installer (.exe)

Standard Windows no installation required (.zip)

The Megapack is identical to the standard Python 3.7 download above, except that it comes with a large number of libraries for scientific computing pre-installed. The Megapack also includes advanced support for JavaScript (code completion, syntax checking, etc.).

Megapack Windows installer (.exe)

Megapack Windows no installation required (.zip)

Some Python packages are not compatible with Python 3. If you want to use those, please download the Python 2.7 (64 bit) package below. Note: As of January 1, 2020, Python 2.7 is no longer maintained.

Python 2 Windows installer (.exe)

Python 2 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.

Python 3 Mac OS package (.dmg)


OpenSesame 3.3 is available through the Cogscinl PPA. Packages are developed and tested on Ubuntu 20.04 Focal Fossa. To add this repository to your software sources and install OpenSesame, run the following commands in a terminal:

sudo add-apt-repository ppa:smathot/cogscinl
sudo apt update
sudo apt install python3-opensesame

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

pip install psychopy expyriment pyspellchecker fastnumbers js2py

Anaconda (cross-platform)

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

conda create -n opensesame-py3 python=3.7  # For Python 2: python=2.7.15
conda activate opensesame-py3

Next, add the relevant channels (cogsci) and (conda-forge) and install all relevant packages:

conda config --add channels cogsci --add channels conda-forge
conda install python-opensesame opensesame-extension-osweb opensesame-plugin-psychopy psychopy rapunzel python-pygaze

Some packages are not available through conda. You can use pip install for these.

pip install soundfile pygame yolk3k opensesame-extension-osf python-qtpip

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 with Python 3.7.6 (standard package) and Python 2.7.15.

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

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.
Supported by Supported by