FYI is an acronym for "For your information." So, instead of writing "For your information" you would simply write "FYI" to get your point across. (Hence, an acronym)

An e-mail may be forwarded and in the content you can write "FYI" and the reader should then scroll down to read the remainder of the e-mail.

Can be mistaken for "For your FYI" - this is misuse of acronym.
Proper use: "The can of corn is in the top shelf, FYI."

Misuse: "For Your FYI it is our boss's birthday today" - wrong.
by Giggles124 January 31, 2014
It's quite simple actually. It was originally a shortened version for For Your Information.

However, people have made up other things that can stand for FYI. For example "Fuck You Idiot". But, that's a bit pointless if you ask me. Saying the whole thing has a grander effect.
(Quoting Shrek 2)

Prince Charming: FYI, not my fault!

Or..

-FYI!!!
-Huh?
-Fuck you idiot!!!
-What the hell?
by HerculePoirot August 28, 2004
FYI means For Your Information... i dunno WTH u ppl are on about; sayin it means Fuck You Idiot... and that crap...it's been on TV, on kid's programmes...on the Simpsons...
Homer Simpson- " FYI- while you two were arguing i ate your breakfasts."
Lisa & Bart together- "D'oh!"
by Adam. J. O. September 1, 2007
person1: 'The sky is green'

person2: 'FYI (For Your Information) its blue'

person1: 'The sky is green'

person2: 'FYI (Fuck You Idiot), its blue'
by FYIMASTER July 12, 2010
Fuck Your Igloo.

Used by young eskimo teenagers who are trying to break away from the traditional eskimo culture.
Mom: You need to go ice fishing with your father!
Eskimo Teen: FYI, MOM
Mom: What?
Eskimo Teen: FUCK YOUR IGLOO goes off to listen to fiddy cent and wear tennis shoes
FYI; Fuck You Idiot. When you're really mad at someone and you think they are so bad at whatever, you say FYI, also meaning For Your Information.
John: Raid Shadow Legends is the best game ever.
Jane: FYI
John: huh?
by eggsbad April 24, 2021