A1Z26 Cipher
Use the CaseSwitch A1Z26 Cipher to map A=1 … Z=26 (and reverse). Choose Encode or Decode, paste letters or numbers, and copy the result. Processing stays in this browser — and this is not cryptography.
Written by the CaseSwitch editorial team. We maintain these tools in the browser so drafts, keys, and images stay on your device.
Last reviewed: 23 July 2026
Processed locally in your browser. Nothing is sent to a server.
Paste or type text to convert. Output stays empty until there is input.
Character count: 0 · Word count: 0 · Line count: 0
Examples
Encode ABC
Input
ABC
Output
1 2 3
Encode HELLO
Input
HELLO
Output
8 5 12 12 15
Decode HELLO
Input
8 5 12 12 15
Output
HELLO
Encode CASE
Input
CASE
Output
3 1 19 5
Decode SOS
Input
19 15 19
Output
SOS
How to use
- Choose Encode (letters → numbers) or Decode (numbers → letters).
- Paste the text or space-separated numbers.
- Copy the result. Remember A=1, not A=0.
What this tool is for
A1Z26 is a classroom cipher: A becomes 1, B becomes 2, through Z=26. Kids and puzzle hunters use it. Nobody should protect a password with it. The tool exists for worksheets and ARG-style puzzles, with an honest security warning.
How it works
Encode keeps A–Z letters (uppercased), maps each to its 1–26 index, and joins with spaces (default separator). Decode reads decimal numbers and maps 1–26 back to A–Z. Numbers outside 1–26 become empty slots. Non-letters are skipped on encode.
When to use it
Worksheets, escape-room handouts, ARG puzzles, and explaining that “codes” are not all encryption.
When not to use it
Never for secrets. Prefer ROT13 only as spoiler obfuscation — still not security. Real confidentiality needs TLS and modern crypto libraries.
How it compares to related tools
Caesar Cipher shifts the alphabet. ROT13 is a fixed Caesar. Base64 is encoding, still not encryption.
Common mistakes
Using 0-index vs 1-index inconsistently (this tool is A=1). Mixing other languages’ alphabets without a mapping. Treating the output as a secure token.
A=1 is the classic rule
Some puzzles use A=0. This tool follows classic A1Z26 (A=1). If a puzzle sheet says otherwise, adjust by hand or the decode will not match the author’s key.
Not encryption
The mapping is public and tiny. Frequency analysis is unnecessary when there are only 26 symbols with fixed numbers. Use it for fun, not for secrets.
Frequently asked questions
Does 1 mean A or does 0 mean A?+
Classic A1Z26 uses A=1. If a puzzle uses A=0, it will not match this tool.
Are spaces encoded?+
Non-letters are skipped on encode. Spaces in the output separate numbers. On decode, only digit groups matter.
Is case preserved?+
Encode uppercases letters before mapping. Decode emits uppercase A–Z.
What about numbers in the plaintext?+
Digits in the plaintext are not letters, so encode skips them. Only A–Z become numbers.
Is this secure?+
No. It is a toy cipher for puzzles and classrooms.
Is my text uploaded?+
No. Conversion runs in this browser.
Does this tool send my payload to CaseSwitch?+
No. Formatting, encoding, and naming conversions for this page run in your browser after load — your sample stays on the device.
Related tools
Caesar Cipher
Teaching frequency analysis, puzzle hunts, classroom demos, and explaining why real crypto uses modern algorithms and keys.
ROT13 Encoder
Hiding movie endings in a forum post, classic Usenet-style spoilers, classroom demos of symmetric trivial ciphers, and quick round-trips to show self-inverse behavior.
Morse Code Translator
Study sheets, escape rooms, short callsign experiments, and demonstrating that “codes” are not all cryptography.