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Caesar Cipher

Encrypt and decrypt with the classic Caesar shift cipher. Includes auto-detect using English letter frequency.

Free No signup Client-side Privacy friendly

Detected shift:

How to use

  1. 1 Pick Encrypt, Decrypt, or Auto-decrypt mode.
  2. 2 For Encrypt/Decrypt, choose a shift (1–25).
  3. 3 For Auto-decrypt, the tool tries all 25 shifts and picks the one closest to English letter frequencies.
  4. 4 Copy the result.

Why use this tool

  • Configurable shift 1–25.
  • Auto-decrypt uses chi-squared scoring against English letter frequency.
  • Preserves case, digits, punctuation, whitespace.
  • Educational tool for cryptography classes.

Frequently asked questions

Is Caesar cipher secure?

No — trivially broken by frequency analysis (try our Auto-decrypt). Use only for puzzles and education, never for actual security.

How does auto-decrypt work?

It tries all 25 possible shifts and computes a chi-squared distance between the resulting letter distribution and standard English. The lowest chi-squared wins.

Why does auto-decrypt sometimes pick the wrong shift?

Auto-detect works best on English plaintext longer than 50 characters. Short inputs or non-English text can mislead the frequency analysis.

Summary

Caesar Cipher is a free developer utility by Zerethon Tools. Encrypt and decrypt with the classic Caesar shift cipher. Includes auto-detect using English letter frequency. Runs entirely in the browser — no signup, no upload.

Category
Developer
Pricing
Free
Privacy
Browser-based
Signup
Not required

Privacy

Your data never leaves your browser unless explicitly stated. Caesar Cipher runs entirely client-side — no server upload, no logging, no tracking of your input.

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