This additional tool to the Remove Duplicates will help you track down all duplicate or unique cells in your Google Sheets.
We care about your data and suggest you always create backup copies of your spreadsheets. A special option of the add-on will do that for you if you select it.
Please bear in mind that Google Sheets limits the total number of possible cells in your file up to 5 million cells.
To compare two sheets or tables for duplicates or uniques, take advantage of the Compare columns or sheets tool instead.
To merge or consolidate unique records that refer to multiple duplicate values on different rows, turn to Combine Duplicate Rows.
Use the Google Sheets menu and go to Extensions > Remove Duplicates > Find duplicate or unique cells:
Choose the range of cells you want to check for duplicates or uniques:
You'll see the entire used range highlighted by default.
Adjust it to your needs by clicking the Select range icon and entering other range manually or selecting it the spreadsheet of interest:
To preserve a copy of your spreadsheet intact just in case, decide in favor of the Create a backup copy of the sheet option.
Click Next to go on to the second step.
Choose the type of data you want to find in your spreadsheet:
Tick off the option to Skip empty cells and the add-on will exclude all empty cells from the search. Otherwise, they will be treated as uniques or duplicates, depending on their frequency within your data.
If you have the same records written in different cases, and you want to have them as different values, check the option to Match case as well.
You can return to step 1 by clicking Back.
Press Next to proceed to the final step.
The add-on offers 4 ways to process the found duplicate or unique cells:
Pick the radio button next to the action you'd like to apply:
Click Finish to find duplicate or unique values.
Once the add-on completes the search, you will see the summary of the result with the number of found values and the action that was applied: