Leetspeak Converter

In short Leetspeak substitutes numbers and symbols for letters that resemble them: 3 for E, 4 or @ for A, 1 for L or I, 0 for O, 7 for T. It began on 1980s bulletin boards, partly as an in-group marker and partly to evade text filters, and the name is itself an example — "elite" became "leet" became "1337". The substitution comes in levels because heavy leet is close to unreadable: light replaces only the obvious vowels and stays legible, medium adds consonants, and heavy uses multi-character substitutions such as |_| for U that turn text into something you have to decode deliberately. Converting back is possible for light and medium and unreliable for heavy, because the substitutions stop being one-to-one — 1 could be L or I, and nothing in the text says which. The practical warning is the one that has aged worst: leet was used to defeat word filters, and no modern filter is fooled by it. Assume anything written in leet is as readable to a machine as plain text.