The A1Z26 cipher assigns a number to each letter of the Latin alphabet based on its ordinal position: A is 1, B is 2, C is 3, and so on through Z which is 26. To encode a message, replace each letter with its corresponding number and separate the values with spaces so multi-digit numbers stay unambiguous. To decode, substitute each number for the corresponding letter. The name "A1Z26" describes the scheme exactly — A maps to 1 and Z maps to 26.
The complete mapping below covers all 26 letters. There is no secret component — the alphabet is public, the rule is public, no key is needed. This makes A1Z26 trivially breakable and unsuitable for protecting information, but straightforward to use in settings where the challenge is recognising the cipher rather than breaking a mathematical system.
How to Encode — Letters to Numbers
Encoding is a letter-by-letter substitution. For each letter, record its position in the alphabet as a number, then separate those numbers with spaces. Spaces are essential: L is 12 and M is 13, so "LM" without spaces becomes "1213" — a decoder could read that as 1, 2, 13 ("ABM") or 12, 1, 3 ("LAC"). Space separation makes the token boundary unambiguous.
The converter is case-insensitive — uppercase A and lowercase a both produce 1. Accented letters fold to their base form before encoding: é and è both count as e (5), ñ counts as n (14), ü counts as u (21). Non-letter characters — spaces, digits, and punctuation — are stripped from the output. "Hello, world!" encodes as 8 5 12 12 15 23 15 18 12 4; the comma and the space between words disappear.
Worked example: HELLO encodes as 8 5 12 12 15 because H is the 8th letter, E is the 5th, L is the 12th (appearing twice), and O is the 15th. Decode that same sequence and you get "hello" back.
How to Decode — Numbers to Letters
To decode, reverse the substitution: look up each number and write the corresponding letter. The Numbers → Letters panel above accepts spaces, commas, and dashes as separators, so 8-5-12-12-15, 8,5,12,12,15, and 8 5 12 12 15 all decode to "hello." Numbers outside the 1–26 range and non-numeric tokens are skipped silently.
Spotting A1Z26 in a puzzle: if every number in a sequence falls between 1 and 26 with no zeros or values above 26, A1Z26 is almost certainly the intended cipher. Values above 26 point to a different encoding — a Polybius square, DTMF tones, or a multi-step cipher where A1Z26 is only one layer.
Where A1Z26 Appears
A1Z26 shows up widely in recreational puzzle contexts because it requires nothing beyond the alphabet — no special tool, no codebook, no prior experience with cryptography.
Geocaching mystery caches embed A1Z26 numbers in the cache description, a hint image, or the coordinates field. Solvers decode them to compute modified latitude and longitude, then navigate to the final waypoint. Puzzle hunt designers use A1Z26 as one layer inside multi-step chains — the decoded text feeds an anagram, a Caesar shift, or a grid read. Escape room designers print numbered cards or number-labelled props for players to decode under time pressure. CTF competitors encounter A1Z26 sequences regularly as standalone beginner challenges or as a first step in a multi-cipher flag.
A1Z26 Is Not a Secure Cipher
A1Z26 provides no cryptographic security. The mapping is fixed, public, and has no key — a brute-force solution takes seconds and frequency analysis breaks any sufficiently long text at a glance. The most common number in an English A1Z26 ciphertext is almost certainly 5 (E), followed by 20 (T) and 1 (A). Do not use A1Z26 to protect sensitive information. For secure communication use TLS; for stored data use AES-GCM with a proper key-management system.
A1Z26 Among Simple Substitution Ciphers
A1Z26, Caesar, and ROT13 are all monoalphabetic substitution ciphers — each plain-text letter always maps to the same output symbol. Caesar shifts letters by a fixed number within the letter domain (a shift of 3 maps A→D, B→E, C→F). ROT13 applies a shift of 13, making the cipher its own inverse so applying it twice restores the original text. A1Z26 converts letters to their decimal ordinal values, producing a number string rather than a letter string. All three are broken trivially by frequency analysis and are used today only for entertainment, light obfuscation, or as one layer in a recreational puzzle. For a related tool, see the Alphabet Counter, which analyses letter frequency in any text.