To find and remove duplicates in Google Sheets, you can use the built-in "Remove Duplicates" feature. Here's how:
1. Open the Google Sheets document that you want to check for duplicates.
2. Select the range of cells that you want to check for duplicates.
3. Go to the "Data" menu in the Google Sheets menu bar and click on "Remove duplicates."
4. In the "Remove duplicates" dialog box, make sure that the "Data has header row" option is checked if your data has headers.
5. Select the columns that you want to check for duplicates by clicking on the checkbox next to each column.
6. Click "Remove duplicates" to remove the duplicate values.
Google Sheets will then remove any duplicate values from the selected columns. Note that the "Remove Duplicates" feature will remove all but one of the duplicate values, so you may want to sort your data first to ensure that the rows you want to keep are preserved.
If you want to highlight the duplicate values instead of removing them, you can use conditional formatting. To do this, select the range of cells that you want to highlight, go to the "Format" menu in the Google Sheets menu bar, and choose "Conditional formatting." From there, you can choose "Custom formula is" and enter a formula to identify the duplicate values, such as "=countif($A$1:$A$100,A1)>1" for a range of A1:A100. Then, choose a formatting option to highlight the duplicates.