What is the difference between basic and advanced leet?

Basic uses common number swaps like a to 4, e to 3 and o to 0. Advanced adds symbol-heavy swaps such as s to dollar sign and i to an exclamation mark for a denser look.

Why does decoding not always match the original?

Leetspeak has no single standard and many letters map to the same symbol, so decoding is a best-effort guess that picks the most common source letter.

Is my text uploaded anywhere?

No. The conversion runs entirely in your browser and nothing is sent or stored.

Leetspeak Converter

Turn text into 1337 5p34k and back, in your browser.

Leetspeak converter — encode and decode 1337

Turn plain text into leetspeak (also written 1337 or l33t) and decode leet back into readable text. Choose basic substitutions for a light, readable style or advanced for a denser, symbol-heavy look.

Leetspeak has no official standard, so decoding is a best-effort guess — everything runs in your browser with nothing uploaded.