Kilowhat v2: browser compatibility

We love the power of web MIDI and we think that MIDI+browsers it’s here to stay. That’s why we developed Kilowhat v2 as a web tool.

We also know not all browsers have MIDI compatibility yet, so this thread will be our place to share any experience regarding Kilowhat and it’s compatibility with different browsers. You can check browser compatibility with Web MIDI API in the site

Let us know your experience so we can keep this thread up-to-date!

Recommended (tested and working)

  • Brave (chromium-based browser with BAT support)
  • Chrome
  • Edge

Could work with (not tested)

1 Like

Adding to this, you can check browser compatibility with Web MIDI API in the site

1 Like

I had an issue with Chrome earlier that Franco helped me fix. It turned out that MIDI sysex was not enabled – I don’t know if I had turned this off or if it defaulted off. To enable it, go to Settings > Privacy and Security > Site Settings > Additional permissions > MIDI devices > flip the switch at the top from “do not allow…” to “ask…”


I have to close Ableton and do a full reboot of my controller to get Kilowhat to recognize my controller… It recognizes my push always, no problem… Kilowhat doesn’t see my Keystep, but disables access to my keystep while it’s open. (denoted by the red)

I am using Chromium, but it’s just Chrome without all the Google crap… On Win10

Steps to reproduce:

1. Start with Ableton open, load Kilowhat in a browser


Note: it recognizes the push, but not my controller or keystep. (not sure if I expect it to recognize the keystep… I wouldn’t expect it to recognize the push yet it does… which would make me think it enumerates all the MIDI devices it finds…)

2. Close Ableton, click “refresh ports”, nothing happens.

3. Unplug the USB port while leaving DC/constant power plugged in, then click refresh, I’m able to select my device in the preferences:

(hmm… it was selected but then it crashed my browser… stay tuned, I’ll get a screen shot)

The popup for where to load the config doesn’t pop up… and when I try to load the config from the device I get an error:

“Could not get device BLOCK 0 to load config”

Actually, sometimes unplugging USB and replugging USB kills Kilowhat and chromium. I use Firefox as my primary browser so fortunately didn’t lose this post!

4. After all of the Above, if I close Ableton, pull the power and USB cable, then plug them back in, I’m able to get Kilowhat working.

EDIT: oh, and when I say it kills Chromium… that’s only sort of correct, because it leaves–whatever the windows version of zombie processes are–running until I unplug the controller. So the UI is closed, but it’s “open” in the background and I can’t start it again until I unplug the controller.

EDIT 2: I think it would be really nice to be able to have Kilowhat and Ableton open at the same time… Maybe there’s reasons that’s not possible? It would be nice to have that/a “workflow” documented somewhere? (maybe it already is?) “Make your changes, push the push and reset button, then close the browser and open your DAW”

I think regardless, there should be “safeguards” to prevent “lockups” (e.g.: detect the controller is in use elsewhere and give the user a message “hey, we can’t do anything until Ableton/“Another Program” gives up control”).

It would be really really nice to have an easy way to transition… I’m working in the app and send the changes to my controller, start my daw, wait for it to load, realize I made a mistake then… have to close the daw, reopen the app… Maybe there could be a “disconnect” or “reset” button in Kilowhat?


Hello @qbrd!

Yeah, Windows doesn’t handle MIDI ports well at all.
You can only open a MIDI port in one application at a time, so mainly that’s what’s going on (I have the same issues).

To use Kilowhat in Windows, you need to close every app using MIDI ports that might hold them open. I think ableton closes them so other apps can use them, but it seems it’s not working for you.

We added the “None” option to the MIDI ports list in Kilowhat, to close all the open ports, but there’s still something we haven’t yet figured out and it’s still not working properly.

The issue with the block 0 alert you got is something we detected and corrected, but still haven’t pushed the changes, but if you try again it should work.

Kilowhat is only supposed to list your Yaeltex controllers, not any other MIDI ports. For this, it sends a sort of “Hello” to all the MIDI ports and waits for a reply. Only Yaeltex controllers will reply correctly, and we’re supposed to close all the other MIDI ports, but like I said, the combination of Windows OS having this limitation for MIDI ports and this handshake process has its subtleties and we’re still sorting them out.

Also, sometimes, Kilowhat will freeze the browser, and like you said, removing USB will get it back up. Another bug we’re aware of and still investigating.

The safeguard message is a good idea, we’ll take that into account and see if there is a way to detect that the ports are open by other applications.

Thanks for reporting all this! Really helps us focus on what we need to work on :slight_smile:

And thanks for the patience!