One out of every seven people on the planet uses the messaging app WhatsApp every day, according a recent blog post from the company. A billion people a day send messages to their friends and family on a service that's end-to-end encrypted by default, up from a billion per month last year. That surge in growth stands in sharp contrast to Twitter, which added approximately no new monthly uses last quarter, and had in fact lost two million in the US.

WhatsApp and Twitter don't just represent contrary growth curves; they're the polar opposites of messaging. Twitter is public. WhatsApp is private. Twitter has a huge problem with safety, while WhatsApp has made privacy and security the center of its mission. And it's now more clear than ever that people have made their choice.

WhatsApples to Oranges

In fairness, Twitter and WhatsApp differ not just in values but also in their fundamental purpose. Twitter is a broadcast service, enabling anyone to share a message with the whole world. WhatsApp is a messenger service, enabling people to talk to people they know. As Pamela Clark-Dickson, an analyst at London-based Ovum, who has followed chat companies closely, puts it: Twitter is a “one-to-many social media site, whereas WhatsApp is primarily a one-to-one communications app (although WhatsApp also enables group messaging, while Twitter also enables direct messaging).”

In some ways, that hamstrings Twitter's potential size. Everyone has people they might want to reach out to directly. Not everyone has something they think they need to share with the world, or understands that they don't need to tweet at all to get a lot of out Twitter. WhatsApp provides a universal service; Twitter's more niche.

“That seems like an apples to oranges comparison to me,” says Andrew Crocker, a staff attorney at the Electronic Frontier Foundation. A more direct comparison would be between WhatsApp and other direct-messaging services, like Facebook Messenger, Signal, Telegram, or iMessage. Of these, WhatsApp has the highest daily users; the next most popular is Facebook Messenger, which boasts 1.2 billion a month.

But instead of raw numbers, look at WhatsApp’s and Twitter’s rates of divergence. Crocker agrees that the explosive popularity of WhatsApp—and other private messaging services—demonstrates just how much people want privacy. That's a stark contrast to just a few years ago, when the death of privacy made for a common refrain in the tech press.

Had that come to pass, Twitter could have become a platform for direct messaging. But save for a few cliques who tweet back and forth to make dinner plans (full disclosure, my mother, and brother, and occasionally myself do this, which others find insufferable), the impersonal interactions Twitter offers have failed to attract an audience. WhatsApp's private space, meanwhile, thrives exponentially.

Privacy Lives

Way back in the pre-Trumpian but post-Snowden era of 2014, headlines like this one were everywhere: Privacy Is Dead. Forbes declared that not only was it dead but it was all of us who use social media that killed it. Mother Jones blamed government surveillance. Even WIRED, coming to privacy’s defense that year, proclaimed that “the rise of publicness has allowed for privateness to become its own trend,” which implied that though privacy was not dead it had become a fetish.

Fast forward to 2017. WhatsApp and Snapchat have become the backlash to the public lives everyone was told were inevitable. Parents turn to WhatsApp to securely share photos of our kids and exchange embarrassing parenting tips. Teens who, as WIRED noted in 2014, once posted to Facebook and then deleted everything as a way to force privacy out of an increasingly public medium, turn more and more to Snapchat or Instagram Stories to communicate ephemerally—scared straight, perhaps, by all the experts who admonished them that their Facebook posts would haunt their college applications and future job prospects.