Alex runs through the features that a progressive web app must have, should have, and would be nice to have.
In general, installability criteria are tightening. Today’s Good-To-Haves may become part of tomorrow’s baseline. The opposite is unlikely because at least one major browser has made a strong commitment to tightening up the rules for installability.
Right now, this is in the nice-to-have category:
Mobile-friendly, not mobile-only.
Personally, I’d put that in the must-have category, and not just for progressive web apps.
Anyway, read on for some advice on testing and tooling when it comes to evaluating progressive web apps.