In 2015, browser push notifications were an exciting new way for websites to notify their visitors when something happened. Unfortunately, the inevitable happened, bad and downright obnoxious UX took over - you couldn't visit a website without being inundated with obnoxious opt-in messages, more often than not before you'd even had a chance to read the page you'd visited.
Firefox recently announced changes to the way they handle these notifications, directly as a result of the misuse by webmasters everwhere.
It's a shame, really. When my team implemented browser push to replace an email we were sending we saw much higher click rates and engagement with the product we were trying to promote.
Ultimately, we've done this to ourselves, I hope Chrome will follow suit soon.