I'm currently using Adobe bridge to cull my old photos and add keywords to them for better searching.

One of the main things in trying to find is a good system of adding keywords and ratings that is tied to the file without any side cars. Is this even possible? Does Photoprism store it's labels in a sidecar or is it editing the exif of the photo?

It would be nice to be able to organize photos in a platform agnostic way.