This is the mirror image of the last remaining cell. Instead of asking where a digit can go, you ask what a cell can hold. Take one empty cell and list the digits already present in its row, its column and its box.
Those three sets overlap, which is what makes the technique work: a cell sits at the intersection of twenty other cells, so it takes surprisingly few filled neighbours to rule out eight digits.
It is slower than scanning per digit, so it is worth reaching for on a specific cell you have a reason to care about — one that would complete a unit, or one that three others depend on — rather than sweeping the grid with it.