Notes on this puzzle
26 digits are printed in this grid and the other 55 cells are yours to fill. A solver that never guesses gets through it in 57 steps.
Most cells fall to the hidden single move: 51 of the 57 steps. Single candidate accounts for 4 more. The toughest moment needs pointing pair, and that single step is what sets the level.
Among the givens, 4 is the most common digit (4 times) and 1 the rarest (2). The emptiest box is the central one, with 0 givens; the top-middle box is the most crowded, with 4.
Where to beginLook at row 5, column 8 first: a hidden single is available there from the very start. Pencil in candidates for one box at a time and watch for two cells that share the same pair.