How to play Codeword

A codeword is a crossword without clues. Every letter of the alphabet has been swapped for a number from 1 to 26, and your job is to crack the code. A couple of letters are given to start you off; the rest you deduce from the shapes of the words.

The rules

1. Each number stands for exactly one letter, and each letter has exactly one number. The same number always means the same letter everywhere in the grid.
2. Every run of white squares across or down is a real word in the chosen language.
3. Some codes are given at the start and cannot be changed: three on Easy, two on Medium and Hard.
4. Not every letter of the alphabet has to appear in the grid.
5. The puzzle is solved when every code used in the grid has the right letter. When you fill the last one, your answers are checked automatically.

Getting started

Click any square to select its code number, then type a letter. That letter appears in every square with the same number, and in the code key beside the grid. Press Backspace to clear it. If you type a letter that is already assigned to another code, it moves to the new code, since a letter can only have one number. You can also click a number in the code key, or click a word in the Horizontal or Vertical list, which shows each word as its run of codes.

Start from the given letters. Suppose the given code 14 is Z, and a three-letter word at row 5, columns 3 to 5, reads 14-7-21. In English a three-letter word starting with Z narrows things fast: ZOO would need the last two codes to match, so with two different codes ZIP or ZAP are likely. Look for another word that uses code 7 to decide between I and A, and the grid starts to unlock.

Strategies and tips

• Read the word patterns. The word lists show each answer as a code sequence. Repeated numbers are gold: a pattern like 3-9-9-3 has a doubled letter in the middle and matching ends.
• Find the vowels. In most languages E, A and O are the most common letters. The numbers that appear most often in the grid are strong vowel candidates, and so are numbers that sit between two different consonant-looking codes.
• Use short words. Three-letter words have few possibilities. Once you have one letter of a short word, the other two are often forced.
• Watch common endings. English words often end in -ED, -ER, -ING or -S; Dutch words often end in -EN. A code that ends many words is worth testing as one of those letters.
• Keep the key in view. The code key shows which letters you have used. When only a few codes are left, the unused letters tell you exactly what remains.
• Check, don't guess blindly. "Check" highlights correct letters in green and wrong ones in red without filling anything in. "Hint" reveals one random code if you are truly stuck.

How the difficulty adapts

Codeword does not change on its own; you set the level. Easy uses an 11×11 grid with three given letters, Medium a 13×13 grid with two, and Hard a 15×15 grid with two. The given letters are always the rarest letters in that particular grid (think J, Q, X or Z), which help a little but never hand you the common vowels. Larger grids have more words and longer words, so Hard needs more careful bookkeeping.

Try stepping up a level when the current one feels routine. The brain seems to benefit most when the challenge keeps rising with your skill, so a puzzle that is always slightly hard is better training than one you solve on autopilot. See what research says about puzzles and brain health.

A short history of Codeword

Codewords combine two old pastimes: the crossword and the substitution cipher, in which each letter is replaced by another symbol. Simple substitution ciphers go back to ancient times, and breaking them by counting how often each symbol appears, known as frequency analysis, was described by Arab scholars more than a thousand years ago. The numbered, clue-free crossword grid is a much more recent puzzle-magazine and newspaper favourite, especially popular in Britain, where it is sometimes sold under names like "code cracker".

Frequently asked questions