A1Z26 Cipher

How to use

1. 1Pick a direction: Encode turns plain text into A1Z26 numbers; Decode turns A1Z26 numbers back into letters.
2. 2For encoding, choose the separator between letters, the separator between words, and how non-letters should be handled.
3. 3For decoding, choose whether the output should be uppercase, lowercase, or preserve the source case (decoder default is uppercase).
4. 4Type or paste your input. The output updates as you type. Use Copy to copy the result or Use as input to round-trip and verify.
5. 5Click Load plain sample or Load cipher sample to see a worked example, or use the A=1 through Z=26 reference grid below for a quick lookup.

About this tool

A1Z26 Cipher is a free in-browser encoder and decoder for the letter-to-number substitution cipher, also known as the alphabet-position cipher. Each Latin letter is replaced with its position in the English alphabet, so A becomes 1, B becomes 2, and Z becomes 26. The mapping is one to one, so the cipher is fully reversible by hand. The encoder lets you pick the character that separates the numbers inside a single word (dash, space, comma, period, pipe, or none) and a separate character that separates whole words (slash, double space, new line, comma plus space, or single space) so the cipher is unambiguous to read back. You can also choose whether non-letter characters like spaces, punctuation, and digits should be kept verbatim, dropped, or replaced with a single space. The decoder is forgiving: it splits on any non-digit so values like 3-1-2, 3 1 2, 3,1,2, and 03 01 02 all decode to cab, and you can ask for the output in uppercase, lowercase, or preserved case (preserved falls back to uppercase because the cipher does not carry case information). Integers outside the 1 to 26 range are surfaced as warnings and replaced with a question mark in the output so you can see where the bad value sat. A reference grid shows the full A=1 through Z=26 mapping for quick lookup. Useful for escape rooms, puzzle books, capture-the-flag challenges, beginner cryptography lessons, and any time you need to translate between letters and their alphabet positions. Everything runs in your browser; the text you paste is never uploaded.

Free to use. Works in your browser. No signup, no login.