For example, Twitter and Google Maps had a plus sign in the address bar and I installed them. I think they are "real" PWAs. I've read that outlook.com in now a PWA, so why doesn't it too have a plus sign in the address bar? I'm using Dev channel Edge.
I do see the "install this site as an app" but is that "really" the same as a PWA?
@DaveLPG outlook is not yet a PWA. I'm not sure if they have a timeline yet for becoming one or not, unfortunately. However, you get basically the same experience when you "install site as an app" as you do from a PWA, the differences are subtle.
In order to get the "Plus" sign in the omnibox for install, three things must be true:
1. the site is served over HTTPS
2. the site has a manifest json file at the root of the domain
3. the site has service workers
You can always go to webhint.io and run a scan on any url to get a "PWA" score.
All that said, we expect that end users will really not be able to tell much difference between a "real" PWA and a site that is installed. Primarily, the differences will come from what would be contained in the manifest, as well as potential offline capabilities.
@johnjansen Thank you for your quick reply and explanation. I think I'll wait till I see a plus sign before I "install" outlook.com. While PWAs sound interesting, they are, at least at the moment, confusing from a user perspective.