R2C1 can only be <9>

R7C4 can only be <3>

R7C6 can only be <5>

R7C7 can only be <6>

R1C1 can only be <5>

R7C3 can only be <8>

R3C3 can only be <2>

R3C4 can only be <9>

R3C7 can only be <1>

R3C6 can only be <8>

R2C5 is the only square in row 2 that can be <3>

R2C9 is the only square in row 2 that can be <4>

R6C2 is the only square in row 6 that can be <5>

R8C8 is the only square in row 8 that can be <5>

R5C1 is the only square in column 1 that can be <7>

R8C5 is the only square in column 5 that can be <7>

R9C5 is the only square in column 5 that can be <4>

R9C1 can only be <1>

R8C4 can only be <2>

R8C6 can only be <1>

R8C1 can only be <4>

Squares R8C2 and R9C2 in column 2 form a simple locked pair. These 2 squares both contain the 2 possibilities <39>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the column.

R4C2 - removing <39> from <1239> leaving <12>

Squares R4C7 and R6C7 in block 6 form a simple locked pair. These 2 squares both contain the 2 possibilities <24>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the block.

R4C8 - removing <2> from <123> leaving <13>

R5C8 - removing <2> from <1268> leaving <168>

R5C9 - removing <2> from <28> leaving <8>

R6C8 - removing <2> from <236> leaving <36>

Intersection of column 9 with block 9. The value <3> only appears in one or more of squares R7C9, R8C9 and R9C9 of column 9. These squares are the ones that intersect with block 9. Thus, the other (non-intersecting) squares of block 9 cannot contain this value.

R9C8 - removing <3> from <239> leaving <29>

Squares R8C2, R8C9, R9C2 and R9C9 form a Type-1 Unique Rectangle on <39>.

R9C9 - removing <39> from <239> leaving <2>

R9C8 can only be <9>

R1C9 can only be <9>

R8C9 can only be <3>

R8C2 can only be <9>

R9C2 can only be <3>

The puzzle can be reduced to a Bivalue Universal Grave (BUG) pattern, by making this reduction:

R4C6=<79>

These are called the BUG possibilities. In a BUG pattern, in each row, column and block, each unsolved possibility appears exactly twice. Such a pattern either has 0 or 2 solutions, so it cannot be part of a valid Sudoku

When a puzzle contains a BUG, and only one square in the puzzle has more than 2 possibilities, the only way to kill the BUG is to remove both of the BUG possibilities from the square, thus solving it

R4C6 - removing <79> from <279> leaving <2>

R4C2 can only be <1>

R4C7 can only be <4>

R2C6 can only be <7>

R6C6 can only be <9>

R5C5 can only be <6>

R4C4 can only be <7>

R6C7 can only be <2>

R5C8 can only be <1>

R1C5 can only be <2>

R6C4 can only be <4>

R5C2 can only be <2>

R4C8 can only be <3>

R6C3 can only be <3>

R1C8 can only be <8>

R1C2 can only be <6>

R2C8 can only be <2>

R2C4 can only be <6>

R4C3 can only be <9>

R6C8 can only be <6>

R2C2 can only be <8>