Microsoft quietly released a distinct new website this week called How-Old.net that uses facial recognition software to guess your age. It's not always right, but it sure makes for a fun way to kill time on the Internet.

At Thursday's Microsoft Build 2015 developer conference, Microsoft officially introduced the site to promote what it's been up to behind the scenes, Business Insider reports. It intends to use similar software to build smarter applications that recognize even slight features in a person's face.

Site engineers Corom Thompson and Santosh Balasubramanian said about the surprise launch, "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 were shocked. Within a few hours, over 35,000 users had hit the page from all over the world."

The site uses loads of data to intelligently guess a person's gender age from a photo under 3MB in size, but it isn't always right.

The app reportedly learns over time, making closer guesses as more users upload and add to the data pool. Essentially, participants take part in training the software, although it's more like a game than an exercise. Many have taken to Twitter to share screenshots of their funny How-Old.net guesses.