X-Wing

An X-Wing is a fish pattern involving four cells arranged in a rectangle. When a digit appears in exactly two cells in each of two rows, and those cells align in the same two columns, the digit can be eliminated from other cells in those columns.

How It Works

The Pattern

Look for a digit that:

Appears in exactly 2 cells in Row A
Appears in exactly 2 cells in Row B
The 2 cells in Row A and the 2 cells in Row B share the same two columns

This forms a rectangle (the "X" shape comes from the two possible solutions crossing each other).

The Logic

If digit 7 can only be in R2C4/R2C8 and R6C4/R6C8:

One of R2C4 or R2C8 must be 7
One of R6C4 or R6C8 must be 7
The 7s in these rows "cover" both columns completely
No other cell in columns 4 or 8 can be 7

How to Spot X-Wings

Single-Digit Focus

The key to spotting fish patterns is focusing on one digit at a time:

Fish	Question	What to Look For
X-Wing	"Where can digit X go in each row?"	2 rows with same 2 columns
Swordfish	"Where can digit X go in each row?"	3 rows with at most 3 columns
Jellyfish	"Where can digit X go in each row?"	4 rows with at most 4 columns

Step-by-Step Scanning

Pick a digit — Choose any digit 1-9
Scan each row — For that digit, count which columns it can appear in
Find pairs — Look for rows where the digit appears in exactly 2 cells
Match columns — Do two rows share the same two columns? That's an X-Wing!
Eliminate — Remove the digit from other cells in those columns

Using Focus Mode

Focus Mode makes X-Wings much easier to spot:

Tap a digit to highlight all cells containing it
Look at each row — does the digit appear in exactly 2 columns?
Compare rows — do any two rows share the same two columns?
If yes, check for eliminations in those columns

Example

Look at digit 7 and ask: where can 7 go in each row?

Row Analysis:

Row 2: digit 7 appears only in R2C4 and R2C8
Row 6: digit 7 appears only in R6C4 and R6C8
Both rows share the same two columns (4 and 8) — this is an X-Wing!

Since rows 2 and 6 "cover" columns 4 and 8, no other cell in those columns can contain 7.

Eliminations: Remove 7 from R1C4, R5C4, R8C4, R9C4, R8C8, and R9C8

puzzle: S9B015y2e685w68050609040i022e0e0f0a2e085y050f0a5u090b042e2u2e0i06042c0810012q0f0dd0015w9i102e020a089e03050f9e0d5y042e05d0609i010f095y0e5y0f0a045y0206020166cy669id205
mode: guided
technique: X-Wing
initial:
  layers:
    hints: true
steps:
  - text: >
      Use Focus Mode to highlight digit 7. Where can 7 go in each row?
    hint: subtle
    technique: XW
    state:
      focus:
        enabled: true
        digits: [7]

  - text: >
      Row 2 has 7 only in columns 4 and 8. Row 6 also has 7 only in columns 4 and 8!
    hint: obvious
    technique: XW
    state:
      selection:
        cells: [R2C4, R2C8, R6C4, R6C8]
      focus:
        enabled: true
        digits: [7]

  - text: >
      These four cells form a rectangle — this is an X-Wing!
    hint: obvious
    technique: XW
    state:
      selection:
        cells: [R2C4, R2C8, R6C4, R6C8]
      focus:
        enabled: true
        digits: [7]

  - text: >
      Rows 2 and 6 "cover" columns 4 and 8. Eliminate 7 from other cells in these columns.
    hint: detailed
    technique: XW
    state:
      selection:
        cells: [R1C4, R5C4, R8C4, R9C4, R8C8, R9C8]
      focus:
        enabled: true
        digits: [7]
settings:
  showCandidates: true
  showControls: true
  showDescription: true
  navigation: numbered

Row vs Column X-Wings

Row-based (as above):

Define rows, eliminate from columns
Find two rows where digit appears in same two columns

Column-based:

Define columns, eliminate from rows
Find two columns where digit appears in same two rows

Both work identically — just swap the dimension.

View in rn-space

An X-Wing involves 2 rows where a digit is confined to the same 2 columns. In rn-space, rows remain rows and columns become digits — so those 2 rows sharing the same 2 column positions appear as a Naked Pair.

This means you can find X-Wings by switching to rn-space and looking for Naked Pairs — a much more familiar pattern. Any Naked Pair you spot in rn-space corresponds to an X-Wing in the standard grid.

puzzle: S9B015y2e685w68050609040i022e0e0f0a2e085y050f0a5u090b042e2u2e0i06042c0810012q0f0dd0015w9i102e020a089e03050f9e0d5y042e05d0609i010f095y0e5y0f0a045y0206020166cy669id205
mode: guided
initial:
  layers:
    hints: false
steps:
  - text: >
      The X-Wing on digit 7: rows 2 and 6 confine 7 to columns 4 and 8.
    state:
      focus:
        enabled: true
        digits: [7]
      selection:
        cells: [R2C4, R2C8, R6C4, R6C8]

  - text: >
      In **rn-space**, this becomes a Naked Pair — rows 2 and 6 for digit 7 share candidates {C4, C8}.
    state:
      space: rn
      focus:
        enabled: true
        digits: [4, 8]
        multiDigitMode: 2+
      selection:
        cells: [R2D7, R6D7]
settings:
  showCandidates: true
  showControls: true
  showDescription: true
  navigation: numbered

Tips

Focus on digits with few candidates — X-Wings are easier to spot when a digit appears in few cells per row/column
Count candidates systematically — For each row, count where each digit can appear
Check alignment — The cells must form a perfect rectangle
Common in medium+ puzzles — Often appears after pointing pairs and box/line reduction

Why "X-Wing"?

The pattern is named after the four cells forming a rectangle. The two possible solutions form an "X" pattern:

One diagonal pair will be 7, the other won't — but either way, columns 4 and 8 are "covered" by rows 2 and 6.

The Fish Family

Fish	Rows/Cols	Pattern
X-Wing	2 × 2	Rectangle
Swordfish	3 × 3	3D pattern
Jellyfish	4 × 4	4D pattern

More Puzzles

Related Techniques

Swordfish — 3×3 version of X-Wing
Pointing Pair/Triple — Simpler intersection technique