The Field Guide · Zip
How to solve Zip faster — the corner-first method
The method in one line
Before you chase a single number, ink the corners. A corner touches only two cells, so unless a number begins or ends the route there, the line is forced to use both connections — free moves that pin the frame of the path before you have reasoned about anything else.
Why corners come first
Zip asks for one continuous line that passes through every cell of the grid exactly once, reaching the numbered cells in order — 1, then 2, all the way to the last number. The line only ever steps between cells that touch edge to edge, never on a diagonal. That single rule is the whole key to solving faster.
Think about how many neighbours each cell has. An interior cell touches four others; an edge cell touches three; a corner cell touches only two. Now picture the line as it travels: every cell it merely passes through is entered once and left once, so it uses exactly two of its connections. The only cells that break that rule are the two endpoints of the whole route — the lowest number, where the line starts, and the highest, where it stops — which use just one.
Put those two facts together. A corner has two neighbours and needs two connections, so — unless that corner is an endpoint — both of its connections are forced. You do not have to deduce them; they cannot be anything else. That is why the corners are the cheapest moves on the board, and why a fast solve starts there rather than at number 1.
| Cell type | Neighbours | Connections forced? |
|---|---|---|
| Corner | 2 | Both, unless an endpoint |
| Edge | 3 | Often, after one is blocked |
| Interior | 4 | Rarely at the start |
The corner-first method, step by step
Run the same four steps on every board and the opening stops being guesswork.
1. Mark the endpoints. Find number 1 and the highest number, and note whether either of them sits on a corner. Those two cells are the only ones allowed to use a single connection; everything else must use two. This is the one check that tells you which corners are special.
2. Ink every non-endpoint corner. For each corner that does not hold the lowest or highest number, draw the line through both of its neighbours straight away. On a 6×6 board with no numbers in the corners, that is up to eight forced segments down before you have thought about order at all.
3. Let the corners chain outward. Once a corner’s two segments are fixed, look at the edge cells beside them. An edge cell has three neighbours; if the line already runs into it from a corner, and one of its other neighbours is blocked, its remaining connection is forced too. These little chains often walk several cells down each edge for free.
4. Only now chase the numbers. With the frame pinned to the corners and edges, connect the numbered stops in sequence. You are no longer drawing into open space — you are joining checkpoints across a path that is already half-built, which is exactly where mistakes stop happening.
The corner that has to wait
Take a common shape: number 1 sits on the left edge, one row above the bottom-left corner, and no number sits in that corner. The tempting first move is to drop straight down from 1 into the corner. The corner-first method tells you why that is a trap before you waste a guess on it.
Because the corner is empty and not an endpoint, its two connections are forced: the line must enter it from the cell above and leave through the cell to its right (those are its only two neighbours). Ink both of those segments first. Now the picture is obvious — the line has to arrive at the corner along one of those edges and depart along the other, so the corner is a pass-through, not a place to dead-end into early.
Solvers who dive in from 1 tend to fill the corner on move two and then strand a single empty cell nearby with no legal way back to it — the classic Zip dead-end. Inking the forced corner segments first makes that mistake impossible, because the route through the corner is already drawn and the line simply has to meet it.
Why this is faster, not just neater
Zip strategy FAQ
Does the corner-first method work on every Zip puzzle?
Almost always. A corner cell has only two orthogonal neighbours, and any cell the path merely passes through has to use exactly two connections — so a corner is forced to use both. The one exception is when a numbered cell that begins or ends the route sits on a corner; then it is an endpoint and uses just one connection.
What if a number sits on a corner cell?
Check whether it is the lowest or highest number on the board. If it is, that corner is an endpoint of the route and uses only one of its two connections, so you cannot ink both. If it is a middle number, the line still passes straight through it and both connections are forced, exactly like an empty corner.
How much time does the corner-first method actually save?
On a 6×6 board it places up to eight forced segments before you have done any real deduction, and those segments often chain into the edge cells beside them. In our own play-testing it removes the early stalls that come from filling a corner too late and stranding an unreachable cell.
Is Zip always solvable with logic alone?
Yes. A well-formed Zip grid has exactly one continuous path that fills every cell and reaches the numbers in order, so every move can be reasoned out rather than guessed. We verify each daily board with a backtracking solver before publishing the answer.
Got the method? Put it on today’s grid.
The reason corner-first feels quicker is that it front-loads certainty. Every forced segment you ink is one you will never have to revisit, and on a tightly built grid those certain moves chain into each other — a fixed corner makes an edge cell forced, which makes the next one forced, and a quarter of the board falls into place before the clock has really started.
It also changes where you spend attention. Instead of staring at number 1 and wondering which way to go, you spend the opening on the cells that can only do one thing, and save your real thinking for the middle of the board, where the genuine choices live. That is the whole game: do the free work first, then think.