Conditional Formatting from another sheet

For some reason (I confess I don't really know why) a custom formula in conditional formatting does not directly support cross-sheet references.

But cross-sheet references are supported INDIRECT-ly:

=A1>INDIRECT("SheetB!A1")

or if you want to compare A1:B10 on SheetA with A1:B10 on SheetB, then use:

=A1>INDIRECT("SheetB!A1:B10")

=A1>INDIRECT("SheetB!"&CELL("address",A1))

applied to range A1:B10.

You can do this by referencing the cell and row number in the current sheet, so as you drag-copy that conditional formatting to other rows it will reference the correct cells. In the below equation I am coloring cells based on the exact same cell in some other sheet named "otherSheetName" in this example. If for example you want to color cell B2 in Sheet2 if the cell B2 in otherSheetName contains the text "I Like Dogs" you would go to cell Sheet2!B2 , click condition formatting, choose equation from the drop down and paste the below equation.

=IF(INDIRECT("otherSheetName!"&ADDRESS(ROW();COLUMN()))="I Like Dogs";1;0)

Comparing strings instead of numbers for a conditional formatting rule, you can use:

=EXACT(A1,(INDIRECT("Sheet2!A1")))

Case sensitive.