Damn. I was so happy to be wrong. Well spotted. I’m back to the “wait for Ionic 4” strategy.
@EvanW - exactly! It is not clear! Those companies are mentioned in Ionic’s PWA discussions/articles but they don’t clearly mention if they are using Ionic. And obviously Ionic guys will not write what technology those companies are using for PWAs.
@AaronSterling - me too, got little excited there. 
It would be great to hear from some Ionic folks, isn’t it?
Maybe @Sujan12 and other from Ionic team can help us.
Thanks.
PWA’s in general are still not widespread, so you can’t blame it all on Ionic. I’m looking in my devtools under “Service workers from other domains” and there are a grand total of 19. Most famous that I’ve got are twitter, google, youtube, the guardian, meetup. Most of the others are developer-oriented websites, including this ionic forum.
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Sorry for the late reply but ionicframework works great on Heroku from my experience. Just copy that www folder to your NodeJS app and that’s it.
Hello,
Not popular 
but I made an application with Ionic3 PWA my site is https://www.picecho.com/ and deploy it on firebase.
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