> Browser Not Supported
  > 
  > PCB Tracer requires a browser that supports access to a local directory.
  > This is needed to save and load your PCB Tracer project files.
  > 
  > Please use Google Chrome or Microsoft Edge for the best experience.

On Firefox, after bypassing the ominous warnings, when I tried to create a new project and choose a directory to save the project files, I get

  > Directory picker is not supported in this browser. Please use a modern browser like Chrome or Edge.

While I appreciate the early warning, so that the user doesn't spend too much effort only to later realize that they can't save their files to disk, I don't appreciate the implicit labeling of Firefox as not being a "modern" browser.

If you're developing a web app with APIs only available in certain browsers, just say/admit so.