IYKYK OR INSIDE JOKE? CONTEXT AND WORDING RECORD
Original Internet Meaning Decoder exercise; these are writing choices, not rules for every group.

The message or situation I am considering:
Is there a joke, a shared experience, or information I do not yet know?
What background makes the reference understandable?
Who already knows that background?
Does the message contain an instruction or fact everyone needs?
What can I explain without sharing someone else's private story or an unwanted spoiler?

Version A — an IYKYK cue, if shared recognition is the purpose:
Version B — name the inside joke, if there really is one:
Version C — explain the background or state the necessary information directly:

Which version fits this audience, and why?
What remains uncertain about the speaker's meaning?
If replying, am I asking about the acronym, the reference, or the practical instruction?

Worked fictional example:
Situation: relatives once applauded before a singer's final note.
Shared cue: Three claps, one unfinished song. IYKYK.
Joke label: The three-clap thing is an inside joke from our family singalong.
Background: We once applauded before the final note, and the singer hadn't finished.
Choice for a new listener: give the background if they want the story.
Limit: knowing the abbreviation does not establish that the listener knows the event.