How can I quickly test someone else's experiment?

How to quickly set up an Empirica experiment locally to test it

You might want to quickly look at someone's experiment, you might be collaborating with others who might not be involved in the coding of the experiment but still want to test it locally, or you might want to copy/tweak these instructions into a file on your repository for people who come across your experiment.

General Setup

If you haven't already:

Preparing their app

Clone the repository with their experiment to a local repository on your device.

In the command line run this to install all the Node packages:

meteor npm install

If you are re-downloading (e.g., you pull from the repository) a version that has had changes in terms of its packages, you need to run this line again.

Running the app locally

You can now run the app on your local machine with:


This can take a few minutes.

This will start the app that you can access as a participant: https:/localhost:3000/

You can access the admin panel here: https:/localhost:3000/admin

Log in with the username and password provided in the command line.

Loading the factors and treatments

To use the app, you usually need to use treatments and factors. Some might be prepared in a .yaml file (e.g., factors.yaml). In the admin panel:

  • click on the Configuration button

  • click on import

  • select the .yaml file you want to import the factors and treatments from

  • wait a few seconds for the factors and treatments to be imported

Testing the app

To run a game create a new batch with the games of treatments you want to use and click start on the batch.

Open a player tab by going to https:/localhost:3000/ or clicking on open app.

The player that you open with https:/localhost:3000/ is cached on your browser. Whenever you start a game with this player, your local app will keep that information. To play again there are multiple things you can do:

  • Click on the Reset current session button on header of a tab with your player to reset this player, and create a new game for this player to join.

  • Click on the New Player button on header of a tab with your player to open a new tab with a different player (you will see tab with an id).

  • Go to the Players tab in the admin panel and retire players that have finished or cancelled.

The app will hot reload as you save changes to the code.