Hidden pairs technique

Strategy #8 for solving Sudoku: Hidden pairs technique

According to the blog author, this strategy definitely ranks among the top tactics for solving Sudoku. This technique is applicable to all variations of classic Sudoku. This strategy works slightly differently in Sudoku puzzles where there are intersections of blocks on the same game board.

Now, let's delve into the hidden pairs strategy itself. First, you need to fill in all empty cells with assumptions of numbers that could be there. On our website, you can do this using notes. Next, you need to consider each 3 by 3 block separately to find two cells containing unique pairs of numbers. If you have found these cells, then this pair of numbers can only be in these two cells, although we don't know exactly which number is in which cell. Therefore, we can eliminate other assumptions that were in these two cells, except for our unique pair.

In the image above on the right, you can see an example of the "Hidden Pairs" strategy in action. Pay attention to the seventh 3x3 block (highlighted in red). Inside this block, there is a pair of numbers 1 and 9 (highlighted in yellow). This pair is unique to the seventh block and appears in only two cells within this block, so we can eliminate other competing candidates from these cells. In the image on the right, we see the result of applying our technique.

Are you ready to take action? Then we invite you to play challenging Sudoku online and try out the new strategy in real life.