It might feel like every person you've ever met is using FaceApp at the moment.
Your timelines have been flooded with people from school posting photos of what they might look like when they're older.
The app has got its critics. There have been warnings over how its creators use your data - and one politician in America even wants the FBI to investigate it.
But how accurate are the app's results? We've put pictures of celebrities from their younger days through it to see how they compare to now.
Sir Ian McKellen
The app is pretty much bang on with Sir Ian McKellen aka Gandalf in The Lord of the Rings.
The picture on the left was taken in his late 20s back in 1968. The one in the middle is after it's been worked on by FaceApp and the right is when Sir Ian played Magneto in X-Men: Days of Future Past - aged 75.
Newsbeat rating: 10/10. Solid.
Sir David Attenborough
Yeah, not too bad.
Taken in 1965, on the left is Sir David Attenborough aged 39. The middle picture is the result after going through the app and on the right is earlier this year aged 93.
Newsbeat rating: 7/10. Good effort.
OK, this is probably not the greatest.
On the left is country singer and all round general icon Dolly Parton in her early 30s back in 1977. Centre is after she's been app'd and the right was earlier in 2019, aged 73.
If anything, she's aged better than the app has done...
Newsbeat rating: 2/10. Requires A LOT of improvement.
Morgan Freeman looks good here - especially in the left picture, which is from 1990 when he was in his early 50s.
But you can't help but feel he's lost a little bit of the glimmer in his eye in the middle FaceApp'd picture. Luckily, it's definitely still there on the right, which was taken in June this year.
Newsbeat rating: 6/10. FaceApp makes Morgan sad.
Dame Judi Dench
On the left, legendary actor Dame Judi Dench aged 33 back in 1967. Middle? You guessed it. After she's been through the app. On the right, in 2019, aged 84.
If anything, we don't think the James Bond actor would be too happy with the results.
Newsbeat rating: 6/10. Try harder.
This is pretty decent, to be fair.
On the left, a picture of a young Austrian actor called Arnold Schwarzenegger in 1976. The middle picture is after he's been processed by the app. On the right, serious politician Arnold Schwarzenegger in a photo taken of him in 2019 aged 74.
Newsbeat rating: 8/10. Pretty impressive.
What is FaceApp?
By Chris Baraniuk, BBC Technology reporter
FaceApp is not new. It first hit the headlines two years ago with its "ethnicity filters".
These purported to transform faces of one ethnicity into another - a feature that sparked a backlash and was quickly dropped.
The app can, however, turn blank or grumpy expressions into smiling ones. And it can tweak make-up styles.
The app also works on painted portraits - although the effect is sometimes unnerving.
It's done with the help of artificial intelligence (AI). An algorithm takes the input picture of your face and adjusts it based on other imagery.
This makes it possible to insert a toothy smile, for instance, while adjusting lines around the mouth, chin and cheeks for a natural look.