IYKYK

abbreviation

informal

if you know you know

—often used to acknowledge some common knowledge or a shared experience

The saying, "If you know, you know," or IYKYK on social media, is being used a lot these days. It's usually associated with postings and events that speak for themselves on the basis of some public knowledge with very little information.

—Dominic Genetti

… Consider Breakfast of Champions, which I read as a teenager and marvelled at the creative use of an asterisk (IYKYK) …

—Andy Brack

While I know it's completely normal, I've always found the borderline beard-level peach fuzz on my face downright annoying. … Oh, and don't even get me started on the one maddeningly resilient black chin hair that reappears after I violently pluck it out each month like clockwork (IYKYK).

—Mia Maguire