L33t

L33t, or leet, is a form of modified spelling used primarily on the internet to substitute letters with numerals or other characters. Originating in the 1980s and 1990s within hacker and bulletin board communities, it spread to gaming, Usenet, and early chat networks as a way to signal skill or identity, as well as to obfuscate text for filters. The term leet derives from "elite," with 1337 often used to represent the word itself.

Substitutions in l33t are highly variable but commonly include A replaced by 4 or @, E by 3, I or L by 1 or !, O by 0, S by 5, and T by 7. Some variants extend to 2 for Z or 8 for B, and users may replace vowels with punctuation or alter spelling to resemble the original shapes. Examples often seen in online culture include h4x0r for hacker and pr0gr4mm3r for programmer. Because there is no single standard, substitutions differ across individuals and communities.

Today, leet remains a cultural reference rather than a practical encoding. Modern technologies and filters have reduced its effectiveness for obfuscation, but it persists in usernames, memes, and stylized branding. It is generally considered a form of stylistic spelling rather than a language, and is studied as part of internet culture and digital communication practices.