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Cipher guides · Substitution

How to Solve the Caesar Shift Cipher

A substitution cipher swaps every letter for another letter and keeps that swap for the whole message. The text still looks like text — same word lengths, same spacing, same doubled letters — it just isn't in English yet.

How to recognise it

Word shapes survive. If you can see one- and two-letter words, an apostrophe, or the same letter doubled in the middle of a word, you are almost certainly looking at a substitution.

Caesar Shift Every letter has slid 3 places down the alphabet. Slide them back.

The key, letter by letter

  • A D
  • B E
  • C F
  • D G
  • E H
  • F I
  • G J
  • H K
  • I L
  • J M
  • K N
  • L O
  • M P
  • N Q
  • O R
  • P S
  • Q T
  • R U
  • S V
  • T W
  • U X
  • V Y
  • W Z
  • X A
  • Y B
  • Z C

A worked example

Message

TREASURE MAP

Key

shift 3

Encoded

WUHDVXUH PDS

Every letter has been swapped for another one, and the same swap is used all the way through. Letter shapes stay put — word lengths and spacing are still real clues. This one is Caesar Shift. The key: shift 3. Every letter has slid 3 places down the alphabet. Slide them back. Take the first letter, W, and walk it back 3 places: it lands on T. Do that to every letter and the message reads T R E… The answer was TREASURE MAP.

Working one out from scratch

Start with the short words and the most common letter. In English that letter is usually E, and a lone letter is usually A or I. Two or three correct guesses tend to collapse the rest of the message on their own.

Caesar Shift days we’ve run

These have closed, so each one carries the full solution. Play them for practice — archive days never touch a streak.

  • Cipher #1 · 31 Aug 2026

    Every letter has been swapped for another one, and the same swap is used all the way through. Letter shapes stay put — word lengths and spacing are still real clues. This one is Caesar Shift. The key: shift 3. Every letter has slid 3 places down the alphabet. Slide them back. Take the first letter, F, and walk it back 3 places: it lands on C. Do that to every letter and the message reads C O U… The answer was COUNT BACK FROM THE GATE.

Now try one

There’s a new cipher waiting today

One a day, three guesses, and a streak that breaks the moment you miss one. Today’s is cipher #12.