Google’s senior vice president of products Sundar Pichai today announced that Gmail now has a total of 900 million users at the company’s annual I/O developers conference. That’s up from 425 million in 2012, the last time the company updated its official Gmail users stats. Pichai also noted that 75 percent of these Gmail users now access their accounts on mobile devices.

When Google last updated its numbers, Gmail became the most popular email service in the U.S. after passing Hotmail (now Outlook.com), which had long held on to the number one spot. Sadly, most of Google’s competitors haven’t updated their user numbers in quite a while. Chances are, though, that Gmail is still at the top of the pack.

Given its success and huge user base, it’s probably no surprise that Google hasn’t made any radical changes to the service. Gmail may have started out as a rather radical reimagining of what a web-based email client should look like. Now that it is the incumbent, Google can’t make any major changes to it without alienating its users.  Instead, it is using Inbox — which sits on top of the Gmail platform — as a space to experiment with what a modern email client should look like.

As Google announced today, Inbox is now open to all users (and has a few new features, too). The company, however, argues that both services serve somewhat different functions and that it remains committed to developing Gmail.