What is the Trick to Solve Sudoku?

You’ve learned the basic rules of Sudoku, but now you’re staring at a puzzle that seems impossible to crack. You’re wondering: is there a secret trick that expert solvers know? The good news is that yes, there are proven techniques and strategies that transform Sudoku from a frustrating guessing game into a logical, solvable challenge.

The truth is, there’s no single “magic trick” to solve Sudoku. Instead, successful solvers use a toolkit of strategies, applying different techniques depending on the puzzle’s difficulty and their current progress. This guide reveals the most effective tricks and methods that will take your Sudoku solving from beginner to expert level.

The Foundation: Scanning is Your Secret Weapon

Before diving into advanced tricks, master the most fundamental technique: systematic scanning. This isn’t glamorous, but it’s the backbone of successful Sudoku solving.

The Three-Way Scan Method

The most efficient scanning approach checks three dimensions simultaneously:

Horizontal Scanning: Run your eyes across each row, noting which numbers are present and which are missing. Look for rows with only one or two empty cells—these are prime targets.

Vertical Scanning: Scan down each column using the same approach. Columns with few empty cells often yield quick placements.

Box Scanning: Examine each 3×3 box to identify missing numbers. Since boxes overlap with rows and columns, they provide a third constraint that often reveals placements you’d otherwise miss.

The trick here is to scan systematically, not randomly. Work through rows 1-9, then columns 1-9, then boxes 1-9. This methodical approach ensures you don’t miss easy placements.

The “One Number at a Time” Trick

Here’s a powerful variation: pick a single number (say, the number 7) and scan the entire grid looking for where that number can be placed. Focus only on finding every possible location for that specific digit.

This concentrated approach often reveals placements that broader scanning misses. Once you’ve placed every possible 7, move to another number. Many expert solvers use this “number-focused scanning” to quickly populate grids, especially with easier puzzles.

The Elimination Technique: Working Backwards

Instead of asking “what number goes here?” ask “what numbers definitely can’t go here?” This shift in perspective is one of the most valuable tricks in Sudoku solving.

How to Use Elimination Effectively

For any empty cell, check its row, column, and box. Cross out every number that already appears in these three regions. What remains are the only possible candidates for that cell.

For example, if a cell’s row contains 1, 3, 5, 7, and 9, its column contains 2 and 4, and its box contains 6, then that cell can only be an 8. You’ve eliminated eight possibilities, leaving only one logical choice.

Pro Tip: Write small “pencil marks” (candidates) in empty cells showing which numbers are possible. As you place more numbers, cross out eliminated candidates. Eventually, cells will have only one remaining candidate—that’s your answer.

The Hidden Single: The Most Overlooked Trick

This technique is where many intermediate players get stuck. A hidden single occurs when a number can only go in one place within a row, column, or box—even though that cell might have multiple pencil mark candidates.

Spotting Hidden Singles

Look at each 3×3 box and ask: “Where can the number 4 go in this box?” If the number 4 can only fit in one cell (because all other cells in that box either already have 4 in their row or column), then that cell must be a 4—even if your pencil marks show other possibilities.

Hidden singles are called “hidden” because they’re not immediately obvious. The cell might show candidates like 4, 6, and 8, but if you check carefully, you’ll discover that 4 is the only number that can go anywhere in that box at position.

The Trick: Systematically check each number (1-9) in each box, asking “where is the only place this number can go?” This reveals hidden singles that casual scanning misses.

The Naked Pair and Naked Triple Tricks

These intermediate techniques dramatically reduce possibilities in a row, column, or box.

Naked Pairs

When two cells in the same region can only contain the same two numbers, those numbers can be eliminated from all other cells in that region.

Example: If two cells in a row can only be 3 or 7 (your pencil marks show “37” in both cells), then no other cell in that row can be 3 or 7. Even though you don’t know which cell is 3 and which is 7, you know those two numbers are “locked” into those two cells.

Naked Triples

The same principle applies to three cells containing the same three candidates. If three cells can only contain combinations of 2, 5, and 8, those three numbers can be eliminated from all other cells in that region.

The Trick: Scan your pencil marks looking for cells with identical or subset candidates. When you spot them, immediately eliminate those candidates from other cells in the same row, column, or box.

The Pointing Pair/Triple Technique

This trick combines box constraints with row and column constraints to eliminate candidates.

How Pointing Pairs Work

If a number can only appear in two or three cells within a box, and those cells are all in the same row or column, then that number cannot appear anywhere else in that row or column outside the box.

Example: If the number 6 can only go in two cells in the top-left box, and both cells are in row 1, then 6 cannot appear anywhere else in row 1 (even in the other boxes). You’ve “pointed” to where 6 must be in that row.

The Trick: After placing numbers in boxes, check if remaining candidates for each number align in a single row or column. Use this alignment to eliminate candidates from cells outside the box.

The Box-Line Reduction Trick

This is the reverse of the pointing pair technique and equally powerful.

How Box-Line Reduction Works

If a number can only appear in one row or column within a box, then that number cannot appear in that same row or column in any other box.

Example: If the number 9 can only go in row 3 within the middle-left box (even though you don’t know exactly which cell in row 3), then 9 cannot appear in row 3 in the top-left or bottom-left boxes.

The Trick: For each box, check if candidates for a particular number are confined to a single row or column. If so, eliminate that number from the same row or column in other boxes.

The X-Wing Pattern: An Advanced Trick

When simpler techniques fail, pattern recognition becomes essential. The X-Wing is one of the most useful advanced patterns.

Identifying an X-Wing

An X-Wing occurs when a candidate number appears in exactly two cells in two different rows, and those cells are in the same two columns (forming a rectangle or “X” pattern).

Example: If the number 5 can only appear in columns 2 and 7 within rows 1 and 6, you’ve found an X-Wing. This means 5 must occupy opposite corners of this rectangle. Therefore, 5 can be eliminated from all other cells in columns 2 and 7.

The X-Wing also works vertically—same two rows within two different columns.

The Trick: When stuck, scan for numbers that appear as candidates in only two positions in two rows. Check if they align in the same columns. This pattern often breaks through seemingly impossible situations.

The “What If” Strategy: Logical Bifurcation

When you’re truly stuck on hard puzzles, systematic exploration can help—but this isn’t random guessing.

Controlled Bifurcation

Find a cell with only two possible candidates. Try one candidate and logically work forward, seeing where it leads. If you reach a contradiction (a cell with no possible numbers, or a violation of Sudoku rules), you know the other candidate must be correct.

Important: Only use this on cells with exactly two candidates, and meticulously track your logic. Use a separate sheet of paper or different colored pencil to distinguish your test moves from confirmed placements.

The Trick: Many solvers avoid this technique because they think it’s “guessing,” but when done methodically with only two options and careful tracking, it’s a legitimate logical technique called “forcing chains.”

The Critical Cell Trick: Start Strong

Where you start in a puzzle significantly impacts your solving efficiency. Expert solvers don’t just dive in randomly.

Choosing Your Starting Point

Begin with regions (rows, columns, or boxes) that have the most given numbers. These areas have fewer possibilities and yield faster results.

Look for:

• Rows or columns with 6+ numbers already filled
• Boxes with 6+ numbers already filled
• Numbers that appear frequently throughout the grid (if 7 appears in seven boxes, finding the remaining two 7s is easier)

The Trick: Spend the first 1-2 minutes surveying the entire puzzle before placing any numbers. Identify the richest targets and attack them first. This strategic start creates momentum and reveals cascading placements.

The Pencil Mark Management Trick

How you use pencil marks dramatically affects your solving efficiency.

Effective Pencil Marking Strategy

Don’t Mark Everything: Only add pencil marks to cells where multiple candidates exist and you can’t immediately determine the answer. Marking every empty cell clutters the grid and slows you down.

Update Continuously: Every time you place a number, immediately scan its row, column, and box to eliminate that number from pencil marks in related cells. Stale pencil marks lead to errors.

Use Small, Neat Marks: Write candidates tiny and consistently in the same position within cells (top-left for 1, top-center for 2, etc.). Organization prevents confusion.

The Trick: Many solvers fail because they either don’t use pencil marks at all or use them inconsistently. Develop a systematic approach and stick with it.

The Fresh Eyes Technique

This might be the simplest yet most effective trick: take breaks.

Strategic Break-Taking

When you’ve been staring at a puzzle for 15-20 minutes without progress, your brain develops tunnel vision. You keep looking at the same cells and missing obvious placements elsewhere.

The Trick: Step away for 5-10 minutes. Get water, stretch, or work on a different puzzle. When you return, scan the grid from top to bottom as if seeing it for the first time. Fresh perspective often reveals placements you repeatedly overlooked.

The Speed-Solving Trick: Prioritize Easy Wins

If you want to solve puzzles faster, adopt the “low-hanging fruit” mindset.

The Progressive Difficulty Approach

Always tackle the easiest placements first. Don’t spend 5 minutes trying to resolve a complex cell when simpler placements are available elsewhere.

Priority Order:

1. Naked singles (cells with only one possible number)
2. Hidden singles (numbers that can only go in one place)
3. Naked pairs and triples
4. Pointing pairs and box-line reduction
5. Advanced patterns like X-Wing

The Trick: After each number placement, rescan the puzzle from the beginning of this priority list. Each new number creates new opportunities at easier levels. Don’t climb to advanced techniques until you’ve exhausted simpler ones.

The Error Prevention Trick

Making fewer mistakes is just as important as finding numbers quickly.

Double-Check Before Committing

Before writing a number permanently (in pen or pressing enter on digital versions), verify it against all three constraints:

• Does this number appear anywhere else in this row?
• Does this number appear anywhere else in this column?
• Does this number appear anywhere else in this box?

The Trick: Use your finger or pencil to physically trace the row, column, and box, checking each cell. This takes 5 extra seconds but prevents errors that might waste 15 minutes.

The Practice Pattern Trick

Want to master Sudoku tricks faster? Practice with purpose.

Focused Technique Practice

Instead of always trying to complete puzzles, occasionally practice specific techniques in isolation:

Naked Pair Practice: Scan completed puzzles to find where naked pairs were used. Train your eye to spot them quickly.

Hidden Single Drills: In a partially completed puzzle, practice finding all hidden singles before making any placements.

Pattern Recognition: Study X-Wing and other advanced patterns in puzzle solution explanations to train pattern recognition.

The Trick: Deliberate practice of individual techniques builds mastery faster than just solving puzzles. Spend 10-15 minutes per week on technique-focused practice.

The Difficulty-Appropriate Strategy Trick

Different puzzle difficulties require different approaches. Using advanced techniques on easy puzzles wastes time; relying only on basic techniques for hard puzzles leads to frustration.

Matching Strategy to Difficulty

Easy Puzzles: Basic scanning and naked singles solve 90% of the puzzle. Use systematic row/column/box scanning.

Medium Puzzles: Add hidden singles, pencil marks for complex cells, and occasional naked pairs.

Hard Puzzles: Full pencil marking, naked pairs/triples, pointing pairs, box-line reduction, and possibly X-Wing.

Expert Puzzles: All of the above plus advanced patterns, forcing chains, and systematic elimination.

The Trick: Assess puzzle difficulty before starting and prepare your mental toolkit accordingly. Don’t overcomplicate easy puzzles or under-prepare for hard ones.

Common Mistakes That Prevent Learning Tricks

Avoid these pitfalls to master Sudoku techniques faster:

Random Scanning: Jumping around the grid randomly instead of working systematically wastes time and causes you to miss placements.

Premature Guessing: Resorting to trial-and-error before exhausting logical techniques prevents skill development.

Ignoring Pencil Marks: Trying to hold all possibilities in your head limits your ability to use intermediate and advanced techniques.

Not Learning from Solutions: Completing a puzzle without understanding which techniques were needed means you won’t recognize those situations next time.

Staying in Your Comfort Zone: Only solving easy puzzles when you’re ready for medium difficulty prevents skill progression.

Combining Tricks: The Expert Approach

The real secret to Sudoku mastery isn’t memorizing individual tricks—it’s knowing when and how to combine them.

The Integrated Solving Process

Expert solvers cycle through techniques in layers:

1. Quick scan layer: Find all naked singles and obvious placements (2-3 minutes)
2. Hidden single layer: Systematically check each number in each box (3-5 minutes)
3. Pencil mark layer: Add candidates to complex cells (3-5 minutes)
4. Elimination layer: Use naked pairs, pointing pairs, and box-line reduction (5-10 minutes)
5. Pattern layer: Look for X-Wing and other advanced patterns (5+ minutes for hard puzzles)
6. Repeat: After placing numbers, return to layer 1 and cycle through again

The Trick: Think in layers, not individual cells. Complete an entire pass through one technique level before moving to the next. This systematic approach is far more efficient than randomly applying whatever trick comes to mind.

Conclusion: Practice Makes Perfect

The ultimate trick to solving Sudoku is understanding that there’s no shortcut to mastery. The techniques in this article scanning, elimination, hidden singles, naked pairs, X-Wing patterns, and strategic pencil marking—are powerful tools, but they become truly effective only through practice.

Start with the foundational tricks: systematic scanning and elimination. Master these on easy puzzles until they become automatic. Then progressively add intermediate techniques like hidden singles and naked pairs. Finally, when you’re comfortable with medium and hard puzzles, explore advanced patterns.

Remember that every expert Sudoku solver was once a frustrated beginner wondering if there was some secret they were missing. The “secret” is simply understanding the logical techniques and practicing them consistently.

The beauty of Sudoku is that it’s entirely logical, no luck, no guessing, just pure deductive reasoning. Every puzzle has a solution that can be found through systematic application of these tricks. Your job is simply to build your toolkit, recognize which tool applies to each situation, and apply it methodically.

Ready to transform your Sudoku solving? Pick up a quality Sudoku puzzle book, start with puzzles slightly above your current comfort level, and deliberately practice these tricks. With each puzzle you solve, these techniques will become more intuitive, your solving speed will increase, and those “impossible” puzzles will become satisfying challenges.

The trick to Sudoku isn’t finding one magic technique, it’s building a complete toolkit and knowing exactly when to use each tool. Now you have that toolkit. Time to put it to work!