Play Word Sieve Online
Every row and every column hides a word, and the number at its end says how long. Cross out the filler letters and see what is left. Warm up on a 4×4 or go hunting on an 8×8: five sizes, three difficulty levels, and one answer to every board.
Created by Brian Hamilton
Tap a letter to cross it out
How to play Word Sieve
Every row hides one word, read left to right, and every column hides one, read top to bottom. The number at the end of a line is the length of its word. The other letters in the line are filler: cross them out, and the letters left standing spell the word in the order they already sit in.
- A letter either stays or goes, and the choice counts for its row and its column at once.
- The letters that stay do not have to be next to each other. They are never rearranged.
- Every line loses at least one letter, and every hidden word has at least three.
- The small number under each clue is how many letters the line has left. It turns to a tick when the count is right — which says the line is the right length, not that it is the right word.
- The hidden words are everyday English, plurals and verb endings included. Nothing you would need a dictionary for.
- Each board has exactly one answer.
Controls: click or tap a letter once to cross it out, again to ring it as part of a word, and a third time to clear it. Right-click rings a letter straight away. Arrow keys move between letters; X crosses out and K rings. Check marks any crossed or ringed letter that disagrees with the answer. You only need to cross out the filler to finish — ringing is for your own notes.
The clue tells you how many readings a line has
A row of five letters with a 4 at its end has exactly one letter too many. There are five letters it could be, so there are five ways to read the row, and you can try all five in your head.
When only one reading of a line is a word, the line is finished: ring its letters, cross out its filler. Call that an only-word line. It is the cheapest deduction in the puzzle and, on a small board, most of the solve.
How many readings there are to try depends on nothing but the length of the line and the clue, and it is worth knowing before you start:
| Board | Clue 3 | Clue 4 | Clue 5 | Clue 6 |
|---|---|---|---|---|
| 4×4 | 4 | – | – | – |
| 5×5 | 10 | 5 | – | – |
| 6×6 | 20 | 15 | 6 | – |
| 7×7 | 35 | 35 | 21 | 7 |
| 8×8 | 56 | 70 | 56 | 28 |
So the biggest clue on the board is the place to start. A 4 on a 5×5 is five readings; a 3 is ten. On an 8×8 nothing is cheap: a line hiding a four-letter word can be read seventy ways, and the skill stops being “try them all” and becomes spotting a likely word and checking that it is the only one.
A worked opening
Here is a 5×5 Medium board, exactly as the builder dealt it. Three of its ten lines have only one reading before anything is marked: row 3, column 2 and column 5.
Row 3 is E, M, O, R, E with a clue of 4, the row drawn above: MORE, and the first E goes. Column 2 is S, A, M, H, E with a 4: SAME, so the H goes. Column 5 is D, Y, E, S, U with a 4: DYES, and the U goes.
Row 2 could not be read on its own. S, A, R, A, Y with a clue of 3 is SAY with either A, or RAY. But column 2 has just ringed the first A, and the only one of those readings that keeps that A is SAY. The R and the second A go. That is the pattern of the whole puzzle: every letter you ring or cross out is a letter decided in two lines at once, and the second line is usually the one that benefits.
Four lines, sixteen cells. This board opens more generously than most: across 300 5×5 Medium boards built for measuring, the only-word rule decides 7.6 cells on average before it first runs out of lines.
When two words fit, keep the letters they share
Now look at what is left. Nine cells are open, six lines are unfinished, and every one of the six is torn between two words:
- Row 1 is USED or SLED. Row 4 is HAS or WAS. Row 5 is EEL or ELM.
- Column 1 is USE or SHE. Column 3 is LOW or OWL. Column 4 is ERA or RAM.
No line can be finished, and guessing is not the answer. Compare the two words instead. USED and SLED disagree about the U and the L, but both of them keep the E. Whichever word row 1 turns out to be, that E stays, so ring it. A letter that every remaining reading keeps is safe; a letter that none of them keeps is filler. These are agreed letters, and they are the second technique.
The E is also the top of column 4, which was ERA or RAM. RAM has no E in it, so column 4 is ERA: ring the A, cross out the M. Row 5 has lost its M and is EEL. EEL rings the L at the foot of column 3, which makes it OWL and crosses out the L at the top. And with that L gone, row 1 is USED. The last line, row 4, can only be WAS.
One agreed letter was enough here, and it usually is: 159 of those 300 5×5 Medium boards need exactly one such step, taking the first one on offer each time, 71 need two and the remaining 70 need three or more. On this board all six unfinished lines offered one, so there were six places to start and they all lead to the same finish.
Second words and doubled letters are what make a board hard
The filler is not random on every board. On Easy it is: each filler letter is drawn at random, weighted the way letters are in the hidden words. On Medium and Hard each filler letter is picked because it lets its row or its column spell some other everyday word through that square. That one change is where USED/SLED and HAS/WAS came from, and it shows in two measurements.
| Board | Difficulty | Could spell a different word | Can spell its own word two ways |
|---|---|---|---|
| 5×5 | Easy | 32.4% | 13.0% |
| 5×5 | Medium | 67.4% | 35.7% |
| 5×5 | Hard | 86.9% | 34.5% |
| 8×8 | Easy | 42.5% | 28.9% |
| 8×8 | Medium | 70.3% | 66.4% |
| 8×8 | Hard | 94.9% | 55.8% |
The first column is the second word: a line that would be perfectly happy as HAS when the answer is WAS. The second is quieter and catches more people. When a letter of the hidden word appears twice in its line, the word can be spelled with either copy, and the line has no opinion about which. S, A, R, A, Y is SAY twice over. You know the word and still do not know the answer, because the answer is a set of squares, not a word. Only the line crossing each copy can tell them apart.
The other thing harder boards do is hide shorter words. That sounds backwards until you look at the first table: a short word in a long line is more filler and more readings.
| Board | Difficulty | Filler | Readings per line | Only-word lines at the start | Boards with none |
|---|---|---|---|---|---|
| 4×4 | Easy | 25.0% | 1.35 | 5.5 of 8 | 0% |
| 4×4 | Medium | 25.0% | 2.12 | 0.4 of 8 | 64.5% |
| 5×5 | Easy | 29.9% | 1.62 | 5.9 of 10 | 0% |
| 5×5 | Medium | 32.0% | 2.64 | 1.2 of 10 | 23.3% |
| 5×5 | Hard | 40.0% | 3.35 | 0.3 of 10 | 70.0% |
| 6×6 | Easy | 26.1% | 1.48 | 8.0 of 12 | 0% |
| 6×6 | Medium | 36.1% | 3.29 | 1.5 of 12 | 14.0% |
| 6×6 | Hard | 43.5% | 4.18 | 0.9 of 12 | 37.6% |
| 7×7 | Easy | 33.5% | 1.84 | 7.5 of 14 | 0% |
| 7×7 | Medium | 37.1% | 3.64 | 1.0 of 14 | 30.0% |
| 7×7 | Hard | 51.4% | 5.93 | 0.5 of 14 | 56.7% |
| 8×8 | Easy | 42.0% | 2.41 | 6.7 of 16 | 0% |
| 8×8 | Medium | 44.7% | 5.28 | 0.7 of 16 | 43.0% |
| 8×8 | Hard | 57.5% | 8.47 | 0.2 of 16 | 85.0% |
Every clue on a 5×5 Hard board is a 3, which is why exactly 40% of it is filler. On an 8×8 Hard board more of the grid is filler than is not, and seventeen boards in twenty give you no only-word line to begin with.
A what-if, worked
The three difficulty buttons are defined by what it takes to finish the board. Easy boards fall to only-word lines from the first square to the last. Medium boards cannot be finished that way and need agreed letters at least once. Hard boards cannot be finished one line at a time at all. This is a 5×5 Hard board, after the two line rules have done everything they can.
Seventeen cells are decided: OIL, ODD, TAP and POD are complete. Eight are open, and every line through them has two readings or more. Row 2 is ADO or BIO, column 1 is BOO or MOO, column 3 is DID or LID, and row 3 is any of MAD, MID, AID and LID. Columns 2 and 4 are doubled letters: TAD with either A, AIL with either I. No two readings of any line agree on an open square, so the second technique has nothing to say.
So ask a question the board can answer. Suppose the L in row 3 stays. Only one of row 3’s four words has an L in it, so row 3 is LID, and the M and the A beside it are crossed out. Column 1 has lost its M: it is BOO, and the B stays. Row 2 now holds a B and an O, so it is BIO, and its A is crossed out. Now read column 2. It needed an A to make TAD, it had two, and both of them have just gone. No word is left. The supposition was wrong, so the L goes — and that is a deduction, not a guess.
With the L crossed out, column 3 is DID, row 2 is ADO, and the last three lines follow one at a time. A what-if is slower than anything else in the puzzle, so save it for when both line rules are stuck, and pick a square where one of the two outcomes forces a whole line, as the L did here. On a 5×5 Hard board one is nearly always enough: of 300 built for measuring, 292 need exactly one, the other eight need two, and the first one runs 4.9 forced steps on average before it breaks.
Where solvers get stuck
Trusting the tick. The small number under a clue counts the letters the line has left, and it turns to a tick when the count matches. That says the line is the right length. S, L, E, D earns the same tick as U, S, E, D.
Taking the first word you find. On a 5×5 Medium board two lines in three could spell a second everyday word, and on Hard it is nearer nine in ten. Finding a word is not the deduction. Finding that it is the only word is.
Choosing between doubled letters. When the word can use either of two identical letters, the line that contains them cannot settle it, and picking the nearer one is a coin toss that the Check button will later charge you for. Ring the letters both spellings share, leave the pair alone, and let the crossing lines decide.
Not re-reading the crossing line. A crossed-out letter is gone from its column as well as its row. The opening above moved only because each finished line was followed straight away by a look at the lines it had just changed.
Four things you can check about these boards
No line keeps all its letters, and no hidden word is shorter than three. A clue is never as big as the line is long, so every row and column has something to cross out, and on a 4×4 every clue is a 3.
Every hidden word has a vowel in it, counting Y. Words like HMM and TSK are left off the list on purpose. So a line with only one A, E, I, O, U or Y in it keeps that letter, whatever its word turns out to be.
On Easy there is always an only-word line, and that holds however many words you know. Easy boards are graded against the whole dictionary, obscure words included: at every stage some line has exactly one reading that is a word of any kind. If you seem to need a comparison on Easy, a line has been misread.
The bar is the builder throwing grids away. Every board is built in your browser when you ask for it: words laid, filler added, and the grid kept only if it passes. Most are ready before the bar can be seen. The slow ones are the Hard boards, because a grid that needs a what-if is a rare find — the builder gets through about 6,200 grids for each 5×5 Hard board it deals — and, oddly, the biggest Easy ones, where fitting sixteen long words that all cross is the hard part and about seventy attempts fail for every one that works. Long searches are shared between up to four of your device’s processor cores. There is no halfway point in a search like that, so the bar shows how likely it is to have finished by now, which is why it slows as it fills instead of stopping somewhere.
The step that matters most happens behind that bar. A board is only dealt if it has exactly one answer when every line is allowed to spell any word of three to six letters in the ENABLE word list, less a short list of slurs — 28,693 words — and not just the 6,458 everyday words the hidden words are drawn from. So an obscure word you happen to know cannot give a second solution. A separate brute-force count, sharing no code with the builder, has re-checked 2,800 of its boards two ways and agrees on every one. Of the 1.5 million 5×5 grids with one answer that the builder graded on the way to those, 305 needed a what-if, about one in 4,900. Among 4×4 grids none did, out of 19,097, which is why there is no Hard button at that size.
The same puzzle under another name
This puzzle is published by Hey, Good Game as Wordplete, developed with the crossword constructor Jeff Chen as the letter counterpart of their number puzzle. The rules here are the same; the boards, the word list and the way difficulty is graded are our own.
The number version is Sumplete, and the difference between them is order. In Sumplete any set of numbers that adds up will do, so a line of five has up to thirty-two candidate answers and the work is arithmetic. In Word Sieve the letters must spell the word as they stand, left to right or top to bottom, so nearly every candidate is dead on sight: a 5×5 Hard line has ten ways to keep three letters and on average 3.35 of them are words. It also differs from a word search, where words run through touching squares in any of eight directions and you are handed the list. Here the letters need not touch, the direction is fixed, and finding out what the words are is the puzzle.
More puzzles where you cross things out
If deciding what does not belong is the part you enjoy, these ask it of numbers: