How to Highlight Duplicates in Excel

1. Highlight the cells you want to check for duplicates. You can highlight a row, a column, any array or non-contiguous group of cells, or the entire worksheet.
2. Click 'Home,' then 'Styles,' and then 'Conditional Formatting' in Excel 2010, or the 'Conditional Formatting' drop-down in the Home tab in Excel 2007.
3. Choose 'Highlight Cell Rules,' then click 'Duplicate Values....'
4. Leave 'Duplicate' selected in the drop-down list of the resulting window, and choose a preset or custom format. Click 'OK' to close the window and view the highlighted results.