Select the range of cells you want to check
Click Format
Click Conditional formatting
Under Format cells if, choose Custom formula is
Enter a duplicate-check formula such as `=COUNTIF(A:A,A1)>1`
Choose a formatting style to highlight duplicates
Click Done
Use the filter or sort options to review highlighted duplicates
To list duplicates in a separate column, use `=IF(COUNTIF(A:A,A1)>1,”Duplicate”,””)`
To remove duplicates, select the range
Click Data
Click Data cleanup
Click Remove duplicates
Choose the columns to check
Click Remove duplicates