Well, some developers have been using .dev as a testing platform for years now on local machines.
Historically, .dev has been the realm of programmers who needed a fake domain for programmer testing. The domain never really existed, they just told their computers to pretend it does. But once Google Registry added .dev to their group of TLDs (which include .app and .page) the days of programmers using .dev for testing were numbered. Even as far back as 2015, savvy developers figured out that Google meant business. And in 2017, Google updated Chrome to add HSTS to .dev
Google Registry offers .dev as a secure domain
Starting today, Google is offering .dev as a secure domain for developers and technology. To ensure that .dev is secure, Google just launched .dev and added the whole TLD to the HSTS preload list. This means registrants will have to provision and set up SSL certificates in order for their content to be loaded in modern browsers.
.dev Registration Schedule
For more information on .dev, go to EnCirca's .dev page