Threads Puzzles
Join each numbered pair with a thread, keep the threads apart, and leave no square of the grid bare.
Hints available. Play as many boards as you like.
Ready when you are.
Scan to open on a phone
Scan for the same board — no hints.
How to play
Every number appears twice. Drag from one dot to its twin to lay a thread, moving one square at a time up, down, left or right — never diagonally, and never through a square another thread already holds.
Drag back along a thread to shorten it, or grab it partway to cut the rest off and take a different route. On a keyboard, arrow keys move the cursor, Enter picks a thread up or puts it down, and Backspace clears the thread under the cursor.
The board is solved when every pair is joined and every square carries a thread. Leaving a square bare is not a near miss — filling the grid is one of the rules, and it is usually the rule that tells you where a thread was wrong.
Strategy
Read the corners first. A corner square has only two neighbors, so whatever thread covers it must arrive along one and leave along the other. If a dot sits in a corner, its thread's first step is already decided; if the corner is empty, some thread has to turn through it.
Work the edges next, for the same reason with one degree less freedom. A thread that steps onto an edge and then steps off again wastes a square that has few ways to be reached, and the squares it skipped often end up unreachable — which is the usual cause of a board that looks finished except for one stubborn gap.
Watch for threads that run alongside themselves. If your route ever ends up next to an earlier part of the same thread, the shorter route through that neighbor was available and the loop you took is dead weight — the squares it wasted have to come from somewhere else. Straightening it out early saves unpicking the whole board later.
When two dots are close together, resist joining them directly. A short thread is cheap, but every square it does not cover has to be covered by a longer thread that may not be able to reach. The threads that look inefficient are usually the ones holding the answer up.
Difficulty and variants
Easy is a 6x6 grid with about six threads, medium an 8x8 with about eight, and hard a 10x10 with about ten. Both numbers climb together: the bigger board also allows longer threads, so a hard board is not merely a larger easy one — it asks you to plan a route of eleven squares rather than six. On a wide screen free play uses a larger set again, up to 12x12.
Questions, answered
What is a Threads puzzle?
A grid with pairs of numbered dots. You connect each pair with a path of horizontally or vertically adjacent squares, no two paths may share a square or cross, and when you are done every square in the grid must be covered.
Do I really have to fill every square?
Yes. Joining the pairs while leaving squares empty is not a solution here. The full-grid rule is what makes the puzzle deducible rather than a matter of taste, because it turns every empty square into a clue about where some thread has to go.
Can a thread cross itself or touch its own side?
It can do neither. A thread is a single walk from one dot to its twin, so no square may be visited twice, and a route that runs back alongside itself would give one of its squares three neighbors of the same color — the board will not accept it.
Is there only one right answer?
Every board is generated from a routing that already covers the grid, so at least one answer always exists. Uniqueness is not enforced, and the check does not compare your board to the stored routing — any set of threads that joins every pair, shares no square and leaves no square bare is accepted. In practice the no-touching and full-grid rules together are strict enough that the boards checked exhaustively each had a single answer.
Are the boards different every time?
Yes. Each puzzle is cut from a fresh seed, and the same seed always produces the same board, so a board can be reproduced exactly if you want to compare notes on one.