How our word searches are made
When you press New game, a fresh grid appears almost instantly. It was not downloaded from anywhere. It was built on your own device, from scratch, in a few thousandths of a second. This is what happens in that time.
Step 1: pick a word list
The site has 64 word lists with 2,048 words between them, from Animals and Breakfast to Castles and knights. The game picks one at random, but skips the last ten lists you played so the same topic does not come round too often. Kids puzzles only use the lists marked as suitable for young players.
Step 2: choose the words
Next it picks words from the list that fit the level. Easy wants words of 3 to 8 letters, Expert takes words up to 14 letters long. One rule matters more than you might expect: no word may sit inside another. If CAT and CATERPILLAR were in the same grid, finding the caterpillar would also show you a cat, and you could mark the cat in the wrong place. The same goes for words hidden backwards inside others, so TAR and STAR would not go together either.
Step 3: place the words
The longest word goes in first, because it has the fewest places it can fit. For each word, the game lists every position and direction that would work: every starting square, every allowed direction, and only spots where any letters it overlaps already match. Then it picks one.
How it picks depends on the level. On Easy, words are mostly kept apart. On harder levels, the game prefers spots where the word crosses another, sharing a letter like a crossword. It also picks the direction first and the position second, so you get a fair mix of directions instead of lots of words running the same way.
Step 4: fill the gaps
The empty squares are filled with random letters. They are not equally likely: E turns up most, Z and Q least, roughly as in ordinary English text. Uniform random letters look wrong, with far too many X's and J's, and make the real words stand out.
Expert does something sneakier. Part of its filler is drawn from the letters of the hidden words themselves, so the grid is full of fragments that look like the start of a word you want.
Step 5: check everything
This is the step that takes the most work. The finished grid is searched along every row, column and diagonal, in both directions, for two things:
- Each word must appear exactly once. Random filler sometimes spells a short word a second time somewhere else. If that happens, you could find a word in the "wrong" place, so the grid is not allowed through.
- The filler must not spell anything rude. There is a short list of words that must never appear in letters we chose at random. A blocked word is allowed only if it sits entirely inside a real hidden word, because CUCUMBER should not be banned for containing three unlucky letters.
If either check fails, the gaps are filled again with new random letters and the grid is checked again. If that keeps failing, the whole grid is started over. Nothing is ever shown until it has passed.
What 10,000 test grids show
We ran the generator 2,000 times at each level and measured the results. These are averages per grid.
| Level | Grid | Words | Squares used by words | Squares shared by two words | Fills tried before one passed |
|---|---|---|---|---|---|
| Easy | 10 × 10 | 8 | 45% | 1.4 | 1.4 |
| Medium | 12 × 12 | 12 | 46% | 6.5 | 1.6 |
| Hard | 15 × 15 | 16 | 38% | 13.5 | 1.6 |
| Daily | 14 × 14 | 15 | 42% | 11.9 | 1.5 |
| Expert | 18 × 18 | 22 | 34% | 24.8 | 2.5 |
A few things stand out. Easy and Medium grids are nearly half real words, which is part of why they feel friendly: almost every other letter belongs to something. Hard and Expert have a lower share because their grids are bigger and their words cross more. On Expert, a typical grid has about 25 shared squares, and it usually takes two or three goes at filling the gaps before one passes every check. The decoy letters that make Expert hard also make it more likely to spell a word twice by accident, so more fills get thrown away.
On Hard, Expert and the Daily puzzle, words are split almost exactly half and half between forwards and backwards, because every one of the eight directions is equally likely.
Why make grids on your device?
Building each grid in the browser means the site never runs out of puzzles, works even on a slow connection once the page has loaded, and does not need to know anything about you. It is also how the Daily puzzle stays the same for everyone: the grid is built from the date, using exactly the same steps on every device, so everyone ends up with the same letters.
Try a fresh grid now, or read the history of word search.