Conditionally formatting cells if their value equals any value of another column

Question

I have data in the A and B columns. B column\'s data is mostly duplicates of A\'s data, but not always. For example:

Answer 1

I unable to comment on the top answer, but Excel actually lets you do this without adding the ugly conditional logic.

Conditional formatting is automatically applied to any input that isn't an error, so you can achieve the same effect as:

=NOT(ISERROR(MATCH(A1,$B$1:$B$1000,0)))

With this:

= MATCH(A1,$B$1:$B$1000,0)))

If the above is applied to your data, A1 will be formatted if it matches any cell in $B$1:$B$1000, as any non-match will return an error.