The Verizon Lumia 735 price is reduced to $30 on-contract for a limited time. Reuters

"How old do you think I am?" The answer was surprising for some of the throngs who tried out Microsoft's new experimental website, launched Thursday – an algorithm-based project that invited users to upload photos of themselves so the site could guess their age. went viral quickly, and thousands posted their results on Twitter, some feeling confident and others questioning what exactly made them appear older. Many even uploaded photos of celebrities, including Jennifer Lopez, Kylie Jenner, Tyga, Lil’ Wayne and Lorde.

How did the site, with its basic orange color and single function, get so popular so fast?

“We were playing with Microsoft’s newly released Face detection API’s through a webpage called This page lets users upload a picture and have the API predict the age and gender of any faces recognized in that picture,” Microsoft said in a blog post on Thursday. “We sent email to a group of several hundred people asking them to try the page for a few minutes and give us feedback – optimistically hoping that at least 50 people would give it a shot. We monitored our real-time analytics dashboard to track usage and, within a few minutes, the number of people using the site vastly exceeded the number of people we had sent our email to. We watched the usage quickly spread across continents, and, 3 hours later…over 35,000 users had hit the page from all over the world (about 29k of them from Turkey, as it turned out – apparently there were a bunch of tweets from Turkey mentioning this page).”

Many non-celebs also participated in the "How old do I look" experiment.

Microsoft explained that it wanted to “create an experiment” that was “intelligent and fun." But it probably wasn’t so fun for users who "looked" older than they actually are.