A1Z26 is one of the simplest substitution ciphers there is: each letter of the alphabet is replaced by its position in the alphabet, so A becomes 1, B becomes 2, all the way up to Z as 26. It shows up constantly in puzzle hunts, escape rooms, and beginner cryptography exercises because it's easy to encode by hand but still requires a small lookup step to read. This tool encodes plain text into space-separated numbers (with a forward slash marking word breaks) and decodes a number sequence straight back into readable text.
Word breaks are encoded as a forward slash "/" so decoding can tell where one word ends and the next begins. Non-letter characters like punctuation are passed through unchanged rather than converted to a number.
No — encoding first converts everything to uppercase, since the cipher only tracks letter position, not case. Decoded output is returned in uppercase letters for the same reason.
Enter numbers separated by spaces, with a "/" token where you want a space between words — for example "8 5 12 12 15 / 23 15 18 12 4" decodes to "HELLO WORLD".