When two people say the same thing at the same time what do people say in France? In English it’s “Jinx!”
My kids and their friends say:
then, if that was simultaneous again:
Double chips !
Triple chips !
and so on until one wins.
When more than two people say the same thing at the same time, one might also say:
Chips personnel !
to win the "contest".
The loser has to stay mute until his/her first name is pronounced by anyone.
Here is a reference: https://warriors-en-savates.skyrock.com/1309936278-La-Loi-du-Chips.html
A "micro-poll" shows that this expression is known by young people between 11 and 20 years old in both Paris area and Brittany but mostly unknown by older people.