The billion-user club used to be exclusive, but it keeps growing.
WhatsApp, the internet messaging service owned by Facebook, announced this week that it now has one billion users worldwide.
That's both a milestone and a potential turning point: Facebook chief executive Mark Zuckerberg has said he thinks internet services are ready to become money-making businesses when they hit that mark.
WhatsApp recently announced it's suspending the nominal fee it charged some users, but it's exploring new ways that other businesses can use WhatsApp to reach their customers.
Meanwhile, Google CEO Sundar Pichai said this week the popular Gmail service now has a billion users, too.
Gmail, which is supported by advertising, joins other Google services with one billion or more users - including Search, Android, YouTube, Maps and Chrome.
Not to be left out, Apple announced last week that there are a billion "active devices" in its ecosystem, which it defines as iPhone, iPad, Mac, iPod Touch, Apple TV and Apple Watch devices that have used the company's online services in the previous 90 days.
Facebook joined the billion-user club in 2012 and now claims 1.59 billion active users a month. Facebook's Messenger service is getting close, with 800 million active users at the end of December, while Facebook's Instagram lags at 400 million.
As for Twitter, it's still struggling with slower growth. The micro-blogging service reports 320 million active users.
