| Reference | Downloads | Github

Running in local debug mode (offline)

I’m struggling to configure psychopy for using the runner to debug experiments offline. I don’t have any experiment yet, just trying to get the demos working. In a fresh install (details below), the runner seems to stop after downloading the JS libraries. That is, I see the following message,

Welcome to PsychoPy3!
39.0988     INFO     Loaded monitor calibration from ['2020_05_03 14:11']
##### PsychoJS libs downloaded to /home/psadil/Documents/psychopy/demos/stroop/html/lib #####

and then nothing else happens (hoping this isn’t just me being inpatient, but at least I waited for 10 minutes).

Thanks for the help

Install Info

OS: Ubuntu 18.04.04 (same situation with fresh hyper-v virtual machine)

extra packages installed

sudo apt install libwebkitgtk-3.0-0 \
                 libcanberra-gtk3-module \
                 libusb-1.0-0-dev \
                 portaudio19-dev \
                 libasound2-dev \

anaconda environment (note: yes, I’m using the 2020.1.3 tag, although the output listed above says v2020.1.2)

name: psychopy
- python=3.6
- pip
- jedi
- pip:
  - git+
  - psychtoolbox
  - pygame
  - pyo
  - pyparallel
pygame 1.9.6
Hello from the pygame community.
2.6559 	INFO 	Loaded SoundDevice with PortAudio V19.6.0-devel, revision 396fe4b6699ae929d3a685b3ef8a7e97396139a4
2.6565 	INFO 	sound is using audioLib: sounddevice
2.6567 	WARNING 	We strongly recommend you activate the PTB sound engine in PsychoPy prefs as the preferred audio engine. Its timing is vastly superior. Your prefs are currently set to use ['sounddevice', 'PTB', 'pyo', 'pygame'] (in that order).
1 Like

Okay. So, yes, it does seem like I was missing a step. It seems like the local debug mode will not run anything until after the experiment has been pushed to pavlovia. Not sure if this was the expected behavior, but hopefully this this thread will help future readers.


  • This was also the case with the standalone version on Windows 10 (2020.1.3)
  • I haven’t actually been able to run the experiment in local debug mode. Although a browser now opens up (chrome), the opened page never moves past “initialising the experiment…”, giving the error copied below. But at least it looks there are a few other threads about similar phenomena.
Failed to load module script: The server responded with a non-JavaScript MIME type of "text/plain". Strict MIME type checking is enforced for module scripts per HTML spec.
1 Like

@psadil, yes it might be useful to have an error message when trying to run local debug on a Builder file without a Pavlovia repo. I am not really sure why you are receiving this error, have JS and HTML files been compiled correctly?

@dvbridges, I certainly would have appreciated an error :slight_smile: .

Re: “failed to load module …” error – as far as I can tell the JS and HTML are fine; I am able to run experiments by piloting from (i.e,. clicking the “Pilot” in the experiment page). It’s just when I try to run PsychoJS in local debug mode that I get this error (edit: I am now working on Windows 10, using the standalone installer).

1 Like

@psadil, I do not seem to be able to replicate the error, would you mind sharing your repository that is causing this problem?

@dvbridges, bummer, but thanks for taking a look. I just started with the stroop demo. Here is the project:

I seem to be having the same issue. I can pilot an experiment but can not locally debug it because of the
"Failed to load module script: The server responded with a non-JavaScript MIME type of "text/plain". Strict MIME type checking is enforced for module scripts per HTML spec." error from the browser. Running Windows 10 and PsychoPy standalone v 2020.1.3 and Chrome.


1 Like