I am really attracted to the idea of local running in-browser tools, since the website is then used only as a distribution medium which is super easy to use. And I really need such a tool, I was eager to test it. However on both my first and second try it failed. I tried to import a video clip recorded on a Pixel phone. In Firefox it failed with a following message:

"Your browser does not support the codec "hvc1.2.4.L156". Try a different video."

Ok, fair, probably need to use Chrome for this type of tool. Tried it in Chrome:

"Audio decode failed: your browser cannot decode the audio in "..._webm.bin". Try re-encoding the file with AAC audio."

Sad. Hope you manage to work this out. Let me know if you have a newsletter or something where I can get notified if this gets fixed.