Excel compare two columns and highlight duplicates

Question

I have an excel file with 10,000 rows in column A some values are the same.

Example:

A1 - P7767

A2 - P3443

A3 - P7767

A4 - P8746

A5 - P9435
         


        

Answer 1

NOTE: You may want to remove duplicate items (eg duplicate entries in the same column) before doing these steps to prevent false positives.

1. Select both columns
2. click Conditional Formatting
3. click Highlight Cells Rules
4. click Duplicate Values (the defaults should be OK)
5. Duplicates are now highlighted in red: