The billion-user milestone is an achievement that lots of tech companies dream of, like billion-dollar valuations or hiring in-house DJs. But most are far from it. For example, Twitter (TWTR) has 310 million monthly active users and LinkedIn (LNKD) has about 106 million.
Google (GOOG), on the other hand, has hit the 1 billion monthly active-user mark several times over. After web browser Chrome reached it in April, the company had seven products that a seventh of the world’s population uses at least once every 30 days.
Not to be outdone, Facebook (FB) has been adding billion-user products quickly in recent years, with Facebook Messenger joining the rarefied club in late July, bringing the company’s total to four and counting.
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Some may quibble with the metric—Netflix (NFLX), for example, has only 83 million members, but unlike Google and Facebook users, they are paying for the service. Still, it’s a handy way of taking stock of Facebook’s and Google’s steady march toward global digital domination.
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A version of this article appears in the September 1, 2016 issue of Fortune with the headline “The Race to 1 Billion Users.”