X-Wing
Short answer: find one shape that fits in exactly two cells of a row, then a second row where it also fits in exactly two cells — in the same two columns. The four cells make a rectangle. Whichever diagonal the shape takes, both columns end up used, so it can be struck from every other cell in those two columns.
What an X-Wing looks like
This is the first technique that stops looking at one unit at a time. Everything up to here — pairs, triples, quads, locked candidates — happens inside a single row, column or box. An X-Wing needs two rows and two columns at once, which is why it stays invisible until you start tracking a single shape across the whole grid.
The name comes from the X you can draw between the two diagonals. Only one of them is real, but you never need to know which — the elimination holds either way, and that is the whole trick.
How to use an X-Wing
- Pick one shape and follow it. Take a single shape and go row by row, noting the rows where it has exactly two possible cells. Ignore every other shape while you do this — mixing them is what makes X-Wings feel impossible.
- Match the columns. Compare those rows in pairs. You want two rows whose candidate cells sit in the same two columns, so the four cells form a rectangle.
- Confirm the corners are the only options. Each of the two rows must have exactly two homes for the shape — not three. If a row has a third, the rectangle proves nothing and the elimination is invalid.
- Strike the two columns. Remove the shape from every cell of both columns outside the rectangle. The same argument works with rows and columns swapped, so check both orientations.
If a pair of rows nearly matches but the columns are one cell off, you may still have something: that near-miss is exactly what a skyscraper is, and it eliminates too. An X-Wing that spans a row and a column instead of two rows is a two-string kite.
X-Wing vs locked candidates
Pointing pairs and box/line reduction also confine one shape to a line, but the argument is contained in a single box. An X-Wing has no box in it at all — the constraint is that two rows both need the shape, and only two columns can supply it, so those columns are fully committed. That is why it is the first technique here that genuinely needs a whole-grid view, and why it is worth learning before the wings and chains that follow.
Find X-Wing in your own grid
Paste a puzzle and this page will look for X-Wing in it — the same pattern shown above, in your grid instead of ours. Nothing is uploaded; it runs in your browser.
Frequently asked questions
Why is it called an X-Wing?
Because of the X you can draw across the rectangle. The shape has to occupy one of the two diagonals — either the top-left and bottom-right corners, or the top-right and bottom-left. You never find out which one, and you never need to: both diagonals use up both columns, which is all the elimination depends on.
Does it work with columns instead of rows?
Yes, and you should check both. If one shape fits in exactly two cells in each of two columns, and those cells share the same two rows, then the shape leaves the rest of those two rows. It is the same pattern viewed sideways, and solvers routinely miss half of all X-Wings by only ever scanning one direction.
What if a row has three possible cells for the shape?
Then there is no X-Wing on that row. The whole argument depends on each row having exactly two homes for the shape — with three, the shape could sit outside the rectangle and the columns are not committed. This is the most common false positive, so count carefully before striking anything.
Is an X-Wing the same as a Swordfish?
Swordfish is the same idea one size up: three rows, three columns, and the shape confined to those columns across all three. X-Wing is the two-row case. If you can see X-Wings reliably, Swordfish is the natural next step, though it turns up far less often.