No codec support for selected audio sources after running fine for 2 months

URL of experiment:
URL of GitHub:

Description of the problem: The study was running properly for 2 months, when suddenly participants are receiving this error:

Unable to download resource: stimuli/sound/Darter9.wav (No codec support for selected audio sources.)

I have tried to update the html but do not know what has changed that the experiment cannot download the audio files. Any ideas on what might have changed?


your experiment is in piloting mode, so nobody except you can test it. You need to make it the gitlab project public and share the link to your gitlab project (or add specific persons as developers).

Best Jens

Oops, thank you! Just added both to the query.


well, the program ran off- and online (Firefox 81, Win 10 20H2) for me. The error message tells you that the browser being used does play not wav-files. Which is strange and does not make a lot of sense because darter9.wav appears quite late in your experiment in block 6.

Sorry, no further idea what is going wrong.

Best Jens

Thanks for the input! It seems really strange. I might just have to try making a new project on pavlovia.

Hi @hmarlatte, could you try using a .wav supporting browser like Chrome? x

Hi @hmarlatte, it would be great if you could give me some more information about the OS / browser combination you are using. I have been unable to reproduce, but brought a couple of edits from the latest version of PsychoPy into the support fork just in case. Could you check below if the problem remains? Thanks, here to help, s.

Thank you for your help! I am use macOS Mojave. The error remains when I use Safari, but things seem loaded when I try on google chrome which is promising.

Thanks for this! I updated things and the problem still persists when I try to run the experiment in safari (which should support .wav files). Any further advice? I suppose I could request participants to run the experiment in Chrome, but that seems like problems could still arise re: compliance. Thanks for all your help with this!

Hi @hmarlatte, no problem! You’re absolutely right Safari is .wav capable, but PsychoJS currently only supports .wav playback on Chrome and that was the case a couple of months ago as well. I have brought the support fork up to date with the latest changes in your own branch, loading in the most recent version of howler.js, the library we rely on for audio support. That should now work on Safari as well :crossed_fingers:

I had the same error message Unable to download resource: … (No codec support for selected audio sources.) only when I try to pilot the experiment using a tablet despite the fact that I am using Chrome on the tablet. What should I do?

Hi @gshejaeya, no worries, would it be possible to share your study with me so I can propose a solution? Here to help, s.

Thank you very much. Here is the link to my experiment:
It is now in the running mode. However, I also cannot download participants’ results directly. I have to go to the Repository then data folder to download the csv files. Is that normal?
Additionally, I will soon upload additional 4 experiments and use Prolific. Will I have the same issues regarding using the tablet and downloading the results with the new experiments?
I appreciate your help.

Hi @gshejaeya, I have staged a support fork to demonstrate a potential fix. Should that be running as expected, I have prepared a merge request for you to accept the corresponding edits into your project. To gather the data files, I believe you can also use the per project download button in the sessions pane on your Pavlovia dashboard,

Thank you so much! This did the trick :smile:

I am seeing the same issue. It’s not clear to me what I need to do to get the fix…

For reference for anyone that still finds this issue, it was fixed by an updated version of the howler JS lib, which was applied to PsychoPy in mid-2020. Please update your version of PsychoPy and regenerate/sync your JS experiment with Pavlovia