Notes on this puzzle
Sudoku #5212 is a medium grid with 31 givens, which leaves 50 cells waiting for a digit. Played purely by logic, it takes 50 forced steps from the first placement to the last.
Most cells fall to the hidden single move: 49 of the 50 steps. Single candidate accounts for 1 more.
Among the givens, 4 is the most common digit (6 times) and 8 the rarest (1). The emptiest box is the central one, with 1 given; the top-left box is the most crowded, with 5.
Where to beginLook at row 3, column 1 first: a hidden single is available there from the very start. When scanning stalls, look for a cell whose row, column and box together rule out eight digits.