Codeword Solver: Fill in the Missing Letters

What Is a Codeword Puzzle?

A codeword is a word puzzle that looks like a crossword grid, but instead of clues, every letter has been replaced by a number. The rule is simple: each number always represents the same letter. Once you figure out that number 5 is the letter E, every 5 in the entire grid instantly becomes an E. The puzzle is solved when every number has been mapped back to its correct letter and the grid is filled with real words.

Codewords appear in newspapers, puzzle books, and online puzzle sites. They are beloved by crossword fans who want a different kind of challenge — one that tests deduction and letter-pattern knowledge rather than general knowledge. The grid is usually 5×5 or larger, and every single cell is part of a word, which means there are no black squares to give you a break.

People get stuck on codewords for a few common reasons: they cannot find a starting point, they have several possible letters for a number and no way to narrow them down, or they have filled in most of the grid but one stubborn word refuses to resolve. That is exactly where this solver helps.

How to Use This Codeword Solver

The solver acts as a digital codeword companion. You tell it what you know about a word in the grid, and it tells you every possible word that fits. Here is the step-by-step process:

1. Pick a word in the grid. Choose any word you want to solve — ideally one where you already know at least one letter.
2. Enter the pattern. Type a 5-character pattern into the pattern box. Use a letter (a–z) for any position you have already solved, and a digit (1–9) for positions you have not. If two unknown positions must be the same letter, give them the same digit. If they must be different letters, give them different digits.
3. Add contains letters (optional). If you know the word must contain certain letters — perhaps from crossing words in the grid — type them into the contains box. This dramatically narrows the results.
4. Click Solve. The solver scans 12,478 five-letter words and returns only those that match your pattern exactly. Results appear as letter tiles below.
5. Use the letter frequency helper. Below the word list, a bar chart shows which letters appear most often in the matching words. This helps you decide which number to try next in the actual puzzle.

Understanding Codeword Patterns

The pattern system is the heart of the solver. It uses a simple convention: a digit represents an unknown letter, and the same digit always represents the same letter. Different digits represent different letters. A letter (a–z) is a known, fixed position. Here are three worked examples to make it crystal clear:

Example 1: Pattern 12134 — The Classic Repeating Pattern

This pattern says: positions 0 and 2 are the same letter (both marked 1), and positions 1, 3, and 4 are all different letters (marked 2, 3, 4). All five positions are unknown, but the first and third must match. Words that fit: ABACK (A-B-A-C-K), PAPER (P-A-P-E-R), RADAR (R-A-D-A-R), TENET (T-E-N-E-T), CIVIC (C-I-V-I-C). Enter 12134 in the solver and you will see all of these plus dozens more.

Example 2: Pattern a2134 — Known First Letter

Here the first letter is known to be A. The remaining four positions are all different unknown groups (digits 2, 1, 3, 4 — the specific digit values do not matter, only that they are different from each other). Words that fit: ABHOR (A-B-H-O-R), ABIDE (A-B-I-D-E), ABORE (A-B-O-R-E), ABUSE (A-B-U-S-E). Note that ABACK (A-B-A-C-K) does NOT fit because positions 1 and 2 are both A, but they have different digits — different digits must be different letters. Enter a2134 and you will see every 5-letter word starting with A where the remaining four letters are all different.

Example 3: Pattern ab1c2 — Two Known Letters

Positions 0 and 1 are known: A and B. Position 2 is unknown (group 1). Position 3 is known: C. Position 4 is unknown (group 2). The two unknown groups must be different from each other. They may or may not equal the known letters A, B, or C — the solver allows a digit to match a known letter (since the known letter has not been assigned to a digit group). Words that fit: ABACI (A-B-A-C-I — group 1 = A, group 2 = I), ABACK (A-B-A-C-K — group 1 = A, group 2 = K). Enter ab1c2 and you will see every 5-letter word starting with AB, with C at position 3, and any letters at positions 2 and 4 (as long as they differ from each other).

Codeword Solving Strategies

Even with a solver, knowing how to approach a codeword makes the process faster and more satisfying. These are the same techniques used by experienced codeword solvers:

• Start with the most common letters. In English, the most frequent letters are E, T, A, O, I, N, S, H, R. If you have a number that appears many times in the grid, it is very likely one of these. Start by guessing that a frequent number is E or A.
• Look for repeating patterns. If you see the same number appearing multiple times in a word — especially in a 5-letter word — think of common repeating patterns like LL (BALL, FILL, TALL), SS (MASS, PASS, KISS), EE (TREE, FREE, AGREE), or OO (BOOK, MOON, FOOD).
• Use crossing words. The beauty of a codeword grid is that words intersect. Once you solve one word, its letters give you clues for every word that crosses it. Always look for the word with the most known letters and solve that first.
• Think about word endings. Many 5-letter words end in common suffixes: -ING, -ED, -ER, -LY, -ES. If you see a number at the end of multiple words, it might be a common ending letter like G, D, R, or S.
• Consider word beginnings. Common starting letters for 5-letter words include S, C, P, T, B, A, F, M, D, and W. If a number appears at the start of many words, it is likely one of these.
• Use the solver to test hypotheses. If you think number 7 might be E, enter a pattern with E in all the 7 positions and see if the resulting words make sense. If the matches are all nonsense, try a different letter.
• Look for short words. If the grid contains any 2-letter or 3-letter words, solve those first. There are only so many 2-letter words in English (OF, TO, IN, IS, IT, BE, AS, AT, SO, WE, HE, BY, OR, ON, DO, IF, ME, MY, UP, AN, GO, NO, US, AM), so they are easy to crack and give you letters for the longer words.

Play Codewords for Free

If you enjoy the deduction challenge of codewords, you will love our free codeword-style games. These games capture the same letter-mapping logic but add their own twist:

• Clueword (Play now) — A reverse word puzzle where you deduce the hidden word from clues. It uses the same letter-pattern logic as codewords but with a unique clue system that makes every puzzle a fresh challenge.
• Chainword (Play now) — Turn every tile into chained words. Chainword combines the crossword feel of codewords with a chain-reaction mechanic where each word you solve unlocks the next.

Both games are free, require no login, and work on any device. They are perfect for sharpening the same deduction skills you use in codewords — and they are a great way to take a break when you are stuck on a particularly stubborn puzzle.

Related Word Tools

If you are stuck on a different kind of word puzzle, we have a full suite of free tools:

• Word Finder (Open tool) — Find every word that matches your letters and pattern. Great for Scrabble, Words With Friends, and crossword puzzles.
• Wordle Solver (Open tool) — Enter your Wordle guesses and their colors to get every remaining possible answer. Handles duplicate letters correctly.
• Anagram Game (Play now) — Make as many words as you can from one set of letters. A fun way to build the vocabulary that makes codeword solving easier.