The technique is based on the rule that 1 digit must appear in a column/row or square 1 time:
In the example below, you see a 3*3 block with values already written into it. Analyze what is in the rows vertically and horizontally. They tell us that the eight in the block of 3*3 we cannot enter in 3 cells horizontally (will be a duplicate) and vertically (will be a duplicate).
Accordingly, we calculate "last remaining cell" by discarding. In this example, it is on the left, vertically. You can consider the block solved and move on to the others!
The method is based on the exclusion of variants. Gradually, by throwing aside cells, we come to the right one. This method is considered basic - it is used by beginners and experienced players, who combine it with others. Once you have mastered the "Last remaining cell" technique, you can move on to the next ones.
Choose techniques from the selection, combine them with each other and create your own approaches to solving simple and hard Sudoku on our site!