This article describes three ways to identify duplicates in Google Spreadsheets.
Google Sheets – Highlight duplicate data in a column or row
The easiest way to clearly see all duplicate cells in Google Sheets is to highlight them. That way, they stand out from the rest of the data set. Here’s how it works with conditional formatting:
Highlight the cells you want to search. If it's an entire column or row, select the letter or number along the edge of the sheet.
Go to Format > Conditional Formatting.
