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Cryptography & Ciphers

A1Z26 Cipher Decoder

Convert separated numbers from 1 through 26 into lowercase English letters. Match the delimiter used in the input.

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Convert separated numbers from 1 through 26 into lowercase English letters. Match the delimiter used in the input.

This tool runs open-source code from CyberChef by GCHQ (Apache License 2.0). See open-source credits.

A1Z26 Cipher Decoder turns numbers from 1 to 26 back into letters, with 1 = a and 26 = z. Choose the delimiter that separates the numbers. 8 5 12 12 15 23 15 18 12 4 decodes to helloworld.

The result is a string of lowercase letters, one per number. It has no spaces unless you add them.

  • Solve a number-code clue from a puzzle hunt or escape room.
  • Check an A1Z26 message you wrote with A1Z26 Cipher Encoder.
  • Read alphabet positions from a worksheet or letter-sum exercise.

Instructions

  1. Paste the numbers into Input.
  2. Choose the Delimiter that appears between them: Space, Comma, Semi-colon, Colon, Line feed, or CRLF.
  3. Run the tool and read the lowercase letters. Add word breaks yourself where they make sense.

Example

Input: 8 5 12 12 15 23 15 18 12 4

Settings: A1Z26 Cipher Decoder with Delimiter Space.

Result: helloworld

A1Z26 Cipher Decoder returns lowercase letters with no spaces. The original word break and punctuation were removed during encoding.

Limits

  • A number below 1 or above 26 stops decoding with an error.
  • A delimiter that differs from the selected one makes the numbers unreadable.
  • Case, punctuation, and word breaks cannot be recovered.

Questions

What does A1Z26 represent?

A1Z26 maps the English alphabet to positions 1 through 26. For example, 1 corresponds to a and 26 to z. It is a fixed alphabet mapping rather than a secret-key cipher.

Which delimiter should I select for A1Z26?

Choose the separator that appears between your numbers or that you want the encoder to insert. Space, Comma, and the other choices create different input boundaries. Use whole-number tokens from 1 through 26 for decoding.

Will A1Z26 preserve punctuation and letter case?

The encoder converts letters to lowercase before mapping them and drops nonalphabet characters. The decoder returns lowercase letters. Keep the original separately if punctuation, spacing, or case matters.