Notes on this puzzle
Sudoku #5210 is a medium grid with 32 givens, which leaves 49 cells waiting for a digit. Played purely by logic, it takes 49 forced steps from the first placement to the last.
Most cells fall to the hidden single move: 48 of the 49 steps. Single candidate accounts for 1 more.
Among the givens, 7 is the most common digit (5 times) and 6 the rarest (2). The emptiest box is the top-left one, with 3 givens; the top-right box is the most crowded, with 4.
Where to beginLook at row 3, column 3 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.