R5C2 can only be <6>

R6C1 can only be <1>

R5C3 can only be <2>

R3C2 can only be <5>

R4C1 can only be <5>

R7C2 can only be <1>

R8C3 can only be <4>

R8C5 can only be <3>

R8C7 can only be <1>

R1C1 is the only square in row 1 that can be <2>

R2C3 is the only square in row 2 that can be <1>

R4C4 is the only square in row 4 that can be <1>

R7C7 is the only square in row 7 that can be <2>

R3C1 is the only square in column 1 that can be <4>

R7C5 is the only square in column 5 that can be <9>

R9C3 is the only square in row 9 that can be <9>

R9C9 is the only square in row 9 that can be <5>

R7C3 is the only square in row 7 that can be <5>

R7C1 is the only square in row 7 that can be <8>

R9C1 can only be <3>

R9C7 is the only square in row 9 that can be <6>

R1C6 is the only square in column 6 that can be <3>

R3C7 is the only square in column 7 that can be <9>

Intersection of row 6 with block 5. The value <8> only appears in one or more of squares R6C4, R6C5 and R6C6 of row 6. These squares are the ones that intersect with block 5. Thus, the other (non-intersecting) squares of block 5 cannot contain this value.

R5C5 - removing <8> from <478> leaving <47>

Intersection of column 5 with block 2. The value <8> only appears in one or more of squares R1C5, R2C5 and R3C5 of column 5. These squares are the ones that intersect with block 2. Thus, the other (non-intersecting) squares of block 2 cannot contain this value.

R1C4 - removing <8> from <478> leaving <47>

Squares R5C5 (XY), R5C8 (XZ) and R3C5 (YZ) form an XY-Wing pattern on <8>. All squares that are buddies of both the XZ and YZ squares cannot be <8>.

R3C8 - removing <8> from <38> leaving <3>

R7C8 can only be <4>

R7C9 can only be <3>

R5C8 can only be <8>

Squares R2C5 and R2C7 in row 2 and R5C5 and R5C7 in row 5 form a Simple X-Wing pattern on possibility <4>. All other instances of this possibility in columns 5 and 7 can be removed.

R1C7 - removing <4> from <478> leaving <78>

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

R1C9=<46>

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

R1C9 - removing <46> from <467> leaving <7>

R1C4 can only be <4>

R1C7 can only be <8>

R3C9 can only be <6>

R6C9 can only be <9>

R3C3 can only be <8>

R6C6 can only be <8>

R4C9 can only be <4>

R9C4 can only be <8>

R2C5 can only be <8>

R1C3 can only be <6>

R2C7 can only be <4>

R3C5 can only be <7>

R5C7 can only be <7>

R5C5 can only be <4>

R4C6 can only be <9>

R6C4 can only be <7>

R9C6 can only be <4>