The short version: start with pearls on corners and edges, then use pearl interactions (adjacent black pearls, rows of white pearls, diagonal patterns). Mark impossible edges with ✕, extend every line end that has only one exit, never close a loop early, and use parity when a region has few exits. Hard puzzles add short “what-if” chains: assume a line, follow the consequences, and reject it if it breaks a rule.
In the diagrams, blue lines are already known, green lines are the new deduction, red ✕ marks edges the loop cannot use, and dashed lines show options still open. If you’re new, read how to play Masyu first.
Black pearl techniques
Black pearls are the strongest clues in Masyu because each one fixes a corner and two straight arms. Most puzzles open with them.
1 Black pearl in a corner
A black pearl in a corner cell can only turn one way. Both arms run along the two edges, two cells each.
2 Black pearl on an edge
A black pearl on the border can’t send an arm off the grid, so its arm perpendicular to that edge must point inward for two cells. The other arm goes left or right — not yet known.
3 Black pearl one cell from an edge
An arm needs two cells. A black pearl in the second row would run out of room pointing toward the edge, so it must point away from the edge. The same applies to the second column from either side.
An arm can’t enter a cell it can’t pass straight through. If the cell two steps away is blocked — by the border, a ✕, or a line running across it — the arm must point the other way.
4 Black arms lock their neighbours
Once an arm is drawn, the cell next to the pearl must be passed straight through, so its two side edges get ✕. The pearl itself turns, so the edge opposite the arm also gets ✕.
5 Adjacent black pearls
Two black pearls side by side can’t connect to each other: the arm from one would have to continue straight through the other, but black pearls must turn. So each sends its horizontal arm away from the other. Vertically adjacent pairs work the same way.
6 Blocked black arm
If the neighbouring cell on one side of a black pearl is already crossed by a line in the other direction, the arm can’t pass through it. The pearl must use the opposite direction.
7 Black pearl with two diagonal white pearls
Put white pearls diagonally on both upper corners of a black pearl. If the black pearl’s arm went up, the cell above it would run vertically, so both white pearls would have to run vertically too — straight down into the cells beside the black pearl. But one of those cells holds the black pearl’s horizontal arm, which runs sideways. Contradiction: the arm must go down.
White pearl techniques
White pearls are weaker on their own, but they combine powerfully — especially in groups and along edges.
8 White pearl on an edge
A white pearl on the border can’t run perpendicular to it (the loop would leave the grid), so it runs parallel to the edge.
9 Two white pearls on an edge
Two adjacent white pearls on the border both run along the edge, so the loop passes straight through both. Each needs a turn beside it, and its inner neighbour is straight — so the loop must turn in the cells just beyond the pair. Next to the edge, those turns point inward.
10 Three white pearls in a row
If three (or more) white pearls sit next to each other in a line, the loop can’t run along that line — the middle pearl would have straight cells on both sides and no turn. So every one of them is crossed perpendicular to the row.
11 White pearl forces the far turn
If the loop already goes straight through the cell on one side of a white pearl, the turn must happen on the other side. Mark ✕ to stop the line continuing straight.
Loop techniques
These techniques ignore the pearls and use the loop itself. On large boards they do most of the work.
12 Dead-end cells
Every cell on the loop has exactly two exits. If a cell has only one possible exit left, the loop can’t visit it — mark ✕ on that last exit as well. This often cascades along corridors.
13 Forced continuation
A line end must keep going. If all but one of its exits are ruled out, draw the line through the only remaining exit.
14 Avoid premature loops
If two ends of the same line segment are next to each other, joining them would close a loop. Unless that loop already includes every pearl and every other line, the edge between them gets ✕. Tracking loose ends is the key skill on 15×15 and larger boards.
15 Parity: even crossings
A closed loop crosses any boundary line an even number of times (it has to come back out of every region it enters — a consequence of the Jordan curve theorem). Draw an imaginary cut across the grid: if one crossing is known, exactly one more among the open edges must exist; if only one open edge remains, it is forced.
A reliable solving routine
- Scan the border. Corner and edge black pearls (techniques 1–3), edge white pearls (8–9).
- Scan pearl groups. Adjacent black pearls (5), rows of whites (10), diagonal patterns (7).
- Lock what you drew. Add ✕ marks around every black arm and finished cell (4, 12).
- Follow every loose end and extend forced lines (13). Re-check each white pearl for a forced turn (11).
- Prevent short circuits (14) and use parity on sparse regions (15).
- Repeat. Each new line usually unlocks another pattern somewhere else.
Hard puzzles: what-if chains
Our Hard puzzles are built so that, at some point, none of the direct patterns above applies. You then need a short contradiction chain:
- Pick an undecided edge near a pearl or a loose end.
- Assume it’s a line (or a ✕) and apply the direct techniques to see what follows.
- If the assumption leads to a rule violation — a dead end, a straight black pearl, a white pearl without a turn, or a small closed loop — the opposite must be true.
This isn’t guessing: you only keep a deduction you’ve proven. Every Hard puzzle on this site was checked by our solver to need nothing deeper than single-step what-if reasoning. Practise on 8×8 Hard before tackling 15×15 Hard.
Turn on “Highlight rule errors” while learning — it instantly shows branches, wrong turns and premature loops. The Check button compares your lines with the solution, and Hint first removes a mistake before adding a new segment.