You can try to explicitly close the unused ports in your Web MIDI application.

I've only played around with Web MIDI a little bit, but I believe Chrome on Windows has a bug: When a tab uses Web MIDI, it will use all the MIDI input and output devices on your system, preventing other apps from using them, until you close the tab -- it doesn't matter if your code closes the port using Web MIDI.

In July 2020 I tried to search if other people had this problem and found the following bug report that seems to describe the issue: https://bugs.chromium.org/p/chromium/issues/detail?id=471793

I haven't done any research on this issue since then, but the up-to-date Chrome on my Windows 8.1 computer still appears to have this bug.

Thank you very much for your answers, I tried closing the ports explicitly with no results.

I will test under my Mac mini to see.

I find this bug (if it is one) very invalidating for the API.
Weird that they didn't correct that.

I will report here the results of my tests under Chrome / Mac.

Thank you again for your posts.

Patrice.

Well ...

It Works on Mac ...

This is a Windows problem ...

Under windows it does not work either under opera ...

We're gonna say it's a bug, eh?

Thank you for your attention .

Patrice;

Try Firefox with the MIDI extension: https://addons.mozilla.org/en-US/firefox/addon/jazz-midi
It also requires the plugin: https://jazz-soft.net/download/Jazz-Plugin

I tried firefox ...

Obviously he doesn't like my code that's not perfect enough for him at all..

If your code uses Web MIDI API, you can either include JZZ.js before your script: https://github.com/jazz-soft/JZZ
or install another plugin: https://addons.mozilla.org/en-US/firefox/addon/web-midi-api