What leetspeak is
Leetspeak, or 1337, swaps letters for numbers and symbols that look like them: e becomes 3, a becomes 4 and t becomes 7, so “leet” becomes 1337. It started on 1980s bulletin board systems and spread through online games and hacker culture, where “elite” users wrote this way.
Basic or advanced?
Basic leet only swaps a few letters for digits, so it stays easy to read: “leet speak” becomes “1337 5p34k”. Advanced leet builds letters out of symbols, like |-| for h and |\/| for m, which looks more cryptic and takes more characters. There is no single correct version; these are common choices.
Leet won’t protect a password
Swapping letters for digits doesn’t make a password safe, because password-cracking tools try these swaps automatically. Use a password manager and long, random passwords instead.