According to nTLDStats.com, it looks like there are now more than 100,000 .Dev domain names registered. I can see more than 102,000 .Dev domain names in the zone file, and the number continues to grow.
The .Dev domain name extension is managed by Google, and .Dev domain names became available to register via the early access program on February 19. Since general availability phase began on February 28, the number of registrations has grown strongly. From what I can tell, it looks like there were about 5,000 domain names registered via the EAP, and in the last week and a half, over 95,000 domain names have been registered.
.Dev domain name registrations aren’t super expensive. It looks like 101Domain charges $13.49/year, Name.com charges $14.99/year, and GoDaddy is charging $13.99/year. There may be special promotional rates offered by some domain registrars, although I have not been tracking that. From what I can tell, it appears that Google has reserved some premium keyword .Dev domain names and charges a higher registration and renewal fee to register them.
Google also manages the .App domain name extension, which has also seen strong growth in the past year or so. There are more than 370,000 registered .App domain names, according to nTLDStats.com.
For those interested in tracking .Dev domain names and seeing some interesting use cases, Google Software Engineer Ben McIlwain has been tweeting about .Dev since they became available to register last month:
— Ben McIlwain (@CydeWeys) February 23, 2019