[arcturus17]

How would they do that if I didn’t log in with Facebook or in any way connect the apps together?

What I did do is add those girls’ numbers on WhatsApp - which is a Facebook property - and they suddenly appeared as friend recommendations.

But if there is any definitive proof it’s that I only was recommended the ones that I had messaged on WhatsApp, never those that I had only chatted up on the Tinder app...

[sopromo]

Each phone has an unique advertisement identifier, they could link you across several apps with that.

But it may be very possible that they do a combination of everything to track you (whatsapp, instagram, facebook, oculus, apps that use the sdk...)