1. Open your Google Sheet and select the column to check
In Google Sheets, highlight the column or cell range where you want to check for duplicates, such as A2:A100.
2. Go to the Format menu and choose Conditional formatting
Click Format in the top menu, then select Conditional formatting to open the sidebar on the right.
3. Apply a custom formula rule to find duplicates
In the sidebar, under Format cells if, choose Custom formula is and enter =COUNTIF(A:A, A2) > 1 if checking column A.
4. Set a highlight style and click Done
Choose a formatting style like a background color to highlight duplicates. Click Done to apply it and instantly flag repeated values.
5. (Optional) Use UNIQUE or COUNTIF formulas to isolate duplicates
To list only duplicates, use =UNIQUE(FILTER(A2:A, COUNTIF(A2:A, A2:A) > 1)) in an empty column.
