[dylan604]

There was another Show HN recently (today?) that explained this. The JS feature to access local file system is currently not available in FF.

https://caniuse.com/native-filesystem-api

[copperx]

I understand, but why does it need filesystem access in the first place?

[dylan604]

so you can upload (er, provide access to) an image of a PCB you are looking to trace

Edit: I should have used a different word than upload. It's just old habit. According to TFA, there is no uploading. All processing is done in the browser, so the app needs local file system access to get at your image