Tinder's law 

The Law of Tinder states if a tinder profile contains a picture with 2 or more people and it's not obvious who the tinderee is, the owner of the account - in almost all cases - is the least attractive person in the picture.

"Hey, I can't tell who Danielle is from her pictures... Who do you think it is"
"Tinder's law man, it's that ugly one on the end"

Tinder's law by Rick James C July 19, 2016

Tinder's Law of Attraction 

On Tinder and similar dating sites, when trying to figure out who the appropriate person is in a group photo, always err on the side of the least attractive person.

Gary: How am I supposed to know which one she is? The only pictures she posted were group photos.

Tim: She is most likely the least attractive person in the group. It's Tinder's Law of Attraction.

Tinder's Law of Attraction by Dr.Daunt June 13, 2015