"hello world" online fails

OS : Apple Silicon
PsychoPy version : 2022.2.5
Standard Standalone? (y/n) :y
What are you trying to achieve?: Initial set-up

What did you try to make it work?: Hello world. I freshly downloaded the standalone Psychopy today, created an experiment in Builder that is nothing more than “Hello World” text, and saved it in an empty folder.

What specifically went wrong when you tried that?:
Local online debugging fails with 404 error:

http://localhost:12002/lib/psychojs-2021.2.3.css is not found
http://localhost:12002/lib/psychojs-2021.2.3.js is not found

It looks like the library that is automatically download on my local machine into the experiment folderwhen I clicked the debug button is: psychojs-2022.2.5.js

For what it’s worth, the experiment runs fine in Python.

Any help greatly appreciated!

Thank you,


Do you have a lib folder? Try deleting it and resyncing.

Apologies for the delayed response-- This is a clean “hello world” test in an empty folder. When I click “debug locally”, a lib folder is created. Deleting it and trying again yields the same result. It seems that the Psychojs files downloaded during the automatic creation of the folder don’t align with what the Builder-to-online code generation expects, as the files in the lib folder are all dated 2023. E.g:


Note that this occurs even after upgrading Pavlovia (Builder version is 2023.1.2).


Try syncing with Pavlovia BEFORE trying to debug locally. Personally I never use the “run the study in PsychoJS in the local browser” option, but my understanding is that this issue is about when you do it.