Crossword Puzzle Generator

How an interlocking crossword is built

A crossword isn't just a list of words — it's a set of words woven together so they share letters at their crossings. This generator takes your own words and clues (two to ten of them) and automatically finds those shared letters to build an interlocking grid you can solve right in the browser. It places the first word horizontally in the center, then for every remaining word it scans every letter already on the grid, looking for a spot where the new word can cross an existing one on a matching letter while running in the perpendicular direction.

The placement algorithm, step by step

For each new word the tool considers every possible intersection with words already placed. A candidate position is rejected unless it passes a validity check: the crossing letters must match, the new word must not run immediately alongside another word (no accidental parallel touching), and it must not extend an existing word at either end. Among all valid positions, it picks the one with the highest intersection score — the placement that shares the most letters with the existing grid. Favoring more crossings produces a tighter, more genuinely interlocked puzzle rather than a loose scatter of barely-connected words.

Because every word after the first must connect through a shared letter, the quality of your word list matters enormously. Words that have common letters in common positions interlock easily; a set with no overlapping letters can't form a crossword at all, and any word the algorithm can't connect is simply left out.

A worked example

Add PLANET, EARTH, and STAR. The generator drops PLANET across the middle. It then looks for somewhere to hang EARTH: both words contain an A and an E, so it can cross EARTH downward through the A in PLANET. Next it tries STAR, which shares a T and an A and an R with what's on the board, and places it crossing one of those letters. The tool then trims the grid to its bounding box, numbers each cell where an Across or Down answer begins, and prints the numbered clue lists beside the grid.

Solving in the browser

Once generated, the puzzle is fully interactive. Click any white square and type; the cursor auto-advances to the next cell to the right, or downward if there's no cell to the right, so you can fill an answer without re-clicking. Check answers colors each filled letter green if correct or red if wrong, letting you spot mistakes without giving away the solution. Show solution reveals every correct letter at once. Nothing is saved — refreshing the page starts fresh.

Tips for puzzles that actually generate well

• Pick words that share letters. Common vowels (A, E, O) and the letters R, S, T, N appear in many words and make great crossing points. A word list rich in these interlocks far more reliably.
• Mix lengths. A few longer words give shorter words more letters to cross through. An all-short-word list leaves little room to connect.
• Letters only. The tool strips anything that isn't A–Z and uppercases everything, so spaces, hyphens, and digits in an answer are removed — keep entries to single plain words.
• Write clues that fit the audience. For a classroom vocabulary quiz, use definitions; for a party puzzle, lean on wordplay. The clue text is shown exactly as you type it.
• If a word goes missing, swap it. A word that won't connect is skipped silently; replace it with one that shares a letter with the words already in your list.

Common mistakes

The most common is entering words with no letters in common and expecting a full grid — the algorithm can only place what it can connect, so you may get fewer words than you typed. Another is using very short two-letter words, which have few letters to cross and often can't be placed. Duplicates are rejected, as are entries without a clue, since every answer needs one to be solvable. Because placement greedily maximises crossings, the exact layout can shift if you add words in a different order — that's expected, not a bug. Everything runs in your browser, so puzzles are private and instant, ideal for teachers, event hosts, and language learners building custom practice.