- Sub-5-minute solving requires a fixed scanning order, not random cell selection
- Start with the most common digit in the givens — it will have the most placements available immediately
- Work all nine digits in one pass before switching to pencil marks
- Fill marks only for cells that are still ambiguous after the digit-scanning pass
- After each placement, immediately re-check the affected row, column, and box for new singles
Phase 1: Count and Prioritize (30 seconds)
Before placing anything, count how many times each digit appears in the given clues. Sort them from most to least common. You will work the most common digits first — they have the most row/column/box constraints already established, making placements easiest to find quickly.
Phase 2: Digit-by-Digit Scan (2–3 minutes)
For each digit, starting with the most common:
- Look at each box that does not yet contain this digit
- For each such box, eliminate cells in rows and columns that already have this digit
- If one cell remains in the box, place the digit immediately
- After each placement, immediately note any newly completed rows/columns for the next scan
Work all nine digits in this order before doing anything else. On an Easy puzzle, this phase alone often solves 25–40 cells.
Phase 3: Fast Pencil Marks (1 minute)
For cells remaining after the digit scan, quickly enter candidates using fast-pencil mode. You do not need to enter all 9 possible digits — only 2–4 are typically still valid per cell at this stage. Focus on cells that look close to being resolved (2–3 candidates).
Phase 4: Hidden Singles Sweep (30 seconds)
Go through each unit and check for any digit that can only go in one cell. These Hidden Singles are almost always present after the digit scan phase. Finding and placing them often creates a cascade of Naked Singles that finishes the puzzle.
Speed Benchmarks
| Difficulty | Beginner | Intermediate | Speed Solver |
|---|---|---|---|
| Easy | 15–30 min | 3–8 min | <2 min |
| Medium | 30–60 min | 8–20 min | 3–6 min |
| Hard | 60–120 min | 20–45 min | 8–18 min |
Practice the Phase 2 digit scan as a drill: pick one digit and time how fast you can find all its valid placements across the nine boxes. Speed in this phase drives overall time more than any other part of the process. Use the Daily Challenge at Easy or Medium for timed practice.