When you're working with data in a spreadsheet, there are often duplicate values that need to be considered. This tutorial will show you how to highlight the repeated items in a few easy steps.

First, highlight the column or row that you want to evaluate.

Click in the top menu then

Conditional formatting menu option
Menu option for conditional formatting

The Conditional Formatting menu option will pop up a menu on the right side of the screen (on the desktop version of Sheets).

Rules for conditional formatting
Rules for conditional formatting

Click the plus sign to begin adding the rule. In the drop-down menu for choose the last option which is .

Custom formula menu option
Last menu option is custom formula

In the box that appears below enter =COUNTIF(A:A,A1)>1. Note that you have to start the formula with a = sign just like any other spreadsheet formula. If you were highlighting a row instead of a column, specify the row as 1:1 if the row were the 1st row.

Custom formula
Custom formula

This will start at A1 and check to see if the value in A1 occurs more than once in the selected range. Then, the conditional formatting goes to the next cell, A2, and so on, until it gets to the end of your specified range. Now, all of the duplicates in your list are highlighted.

The A:A may seem a little strange but this is a method of specifying an entire column no matter how many rows are used.

Result
Result with highlights duplicated

Video explanation

Follow image below for the live Google Sheet with this data

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