A Microsoft website is suddenly the hottest thing on the internet.
The premise is very simple - you upload a photo on how-old.net and it magically determines the age and gender of the person featured in that image.
Now, many of us like to think age is just a number but let's face it, we still care about how old we look.
And that's part of the reason why the site has taken off.
Another reason for its popularity is that you can upload anyone's image. Users are having quite a bit of fun uploading images of celebrities.
The website uses facial analysis algorithms according to a Microsoft blog post.
There's a huge variation in terms of accuracy and the site has an apologetic message in the end with a note that they will continue to improve the service.
More from AOL.com:
Homeless man donates 18 cents to church with touching note
How a clean bedroom makes for a happy life
'I can't believe it!' Dog owner reunited with her pet after 4 years and 940 mile journey