Sudoku Tips & Strategy: From First Grid to Expert
Once you know the rules, improving is mostly about learning to recognise a handful of patterns. Here are the techniques that take you from Easy boards all the way to our Evil level, roughly in the order you should learn them.
Before anything: solve in the right order
Beginners often jump around the grid at random. A better habit is to work the easiest wins first and only reach for harder techniques when the simple ones dry up. The ladder below follows that order. On any given puzzle, keep cycling back to the top of the ladder after each placement — an easy move often reappears once you have filled a cell or two.
Technique 1: Scanning (cross-hatching)
Scanning is the foundation. Pick a digit and look at where it already appears. Each existing copy of that digit “casts a shadow” down its column and across its row, blocking the digit from those cells. When you focus on a single box, those shadows often leave just one legal cell for the digit. This is the fastest way to fill Easy and Medium boards, and it costs you nothing to do in your head.
A practical tip: work through the digits 1 to 9 in order, scanning the whole board for each. It feels mechanical, but it is remarkably effective and rarely misses an obvious placement.
Technique 2: Naked singles
A naked single is a cell that has only one candidate left. If a cell’s row, column, and box between them already contain eight different digits, the ninth is forced. Keeping pencil notes makes naked singles jump out: any cell showing a single pencil mark is a guaranteed move. Turn on notes mode with the pencil button or the N key to track this automatically as you fill the grid.
Technique 3: Hidden singles
A hidden single is sneakier. It is a cell where a digit can go, and crucially it is the only cell in that row, column, or box where that digit can go — even though the cell itself may still show several candidates. To find them, pick a unit and a digit, and check how many cells in the unit could hold it. If the answer is exactly one, you have found a hidden single. These unlock most Hard puzzles.
Technique 4: Naked pairs and triples
When two cells in the same unit share the exact same two candidates — say both can only be 4 or 7 — then 4 and 7 are “claimed” by those two cells. Neither digit can appear anywhere else in that unit, so you can safely erase 4 and 7 from the other cells’ notes. This often creates a new naked single elsewhere. The same idea extends to three cells sharing three candidates (a naked triple).
Technique 5: Pointing pairs
Sometimes within a box, a digit’s only possible cells all sit in the same row or the same column. When that happens, the digit must end up in that row or column inside this box, which means it cannot appear in the same row or column outside the box. You can remove it as a candidate from those outside cells. Pointing pairs are a staple of Expert and Master solving.
Technique 6: Box/line reduction
This is the mirror image of a pointing pair. If, within a single row or column, a digit can only appear in cells that happen to share one box, then the digit is locked into that box for that line — and can be erased from the rest of the box. Spotting both directions of this interaction is what separates confident solvers from the rest.
Technique 7: When you reach Evil
Our toughest boards occasionally need advanced patterns such as X-Wings and colouring. An X-Wing, for example, looks at a digit that is confined to the same two columns across two separate rows; that rectangle lets you eliminate the digit from those columns elsewhere. You do not need these for most puzzles, and when you do, the earlier techniques will have already narrowed the grid enough to make them visible. Take your time — Evil puzzles reward patience far more than speed.
Good habits that help at every level
- Keep your notes honest. Update candidates as soon as you place a number, so your pencil marks never lie to you.
- Use the highlight. Tapping a number on vSudoku shows every matching cell, which turns scanning from a chore into a glance.
- Work in passes. Do a full scan of all nine digits, then a full naked-single pass, then hidden singles, and loop back. Systematic beats scattered.
- Step away when stuck. A fresh look often reveals a move you stared straight past. The Undo button means you can always experiment safely.
- Resist guessing. Every move has a logical reason. If you cannot find it, an earlier technique usually has an unspotted answer.
Practise deliberately
The quickest way to improve is to play a level slightly above your comfort zone and focus on one new technique at a time. Start a Medium or Hard puzzle and try to finish it using hidden singles rather than hints. When that feels natural, move up. If you are still getting comfortable with the basics, the how-to-play guide is the best place to begin.