I don't know the technical details behind this, but Firefox always felt slower in file upload front. It was very late to the directory upload feature that Chrom

I don't know the technical details behind this, but Firefox always felt slower in file upload front. It was very late to the directory upload feature that Chrome had (in mostly non-standard ways I don't doubt). It doesn't bother me to a point that I can't use Firefox, but for those who regularly upload files, I can totally see Firefox being a subpar experience.