Spot the Double. How to Find Duplicates in a Column in Google Sheets

Finding and removing duplicate entries in a column is a common task in spreadsheet management. Google Sheets provides several methods to identify duplicates, both manually and through custom script automation. In this article, we will explore both approaches and provide step-by-step instructions.

Manually Finding Duplicates in Google Sheets

To manually find duplicates in a column in Google Sheets, follow these steps:

Open your Google Sheets document and navigate to the sheet containing the column you want to search for duplicates in.
Select the column by clicking on the letter at the top of the column.
In the menu bar, click on "Format," then select "Conditional Formatting."
In the conditional formatting sidebar that appears on the right, choose "Custom formula is" from the drop-down menu.
Enter the following formula into the input field: =countif(A:A, A1)>1, replacing the A:A with the range of your column, and A1 with the first cell of your selected column.
Choose the desired formatting style to highlight the duplicates. For example, you can set the background color or text color to make the duplicates stand out.
Click "Done" to apply the formatting.

After following these steps, any duplicate entries in the selected column will be highlighted based on the formatting you chose.

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Automating Duplicate Detection with Google Apps Script

If you frequently deal with large datasets and want to automate the process of finding duplicates in a column, you can utilize Google Apps Script. With scripting, you can create custom functions that perform the duplicate detection automatically.

To detect duplicates using Google Apps Script, follow these steps:

Open your Google Sheets document and navigate to the sheet containing the column you want to search for duplicates in.
Click on "Extensions" in the menu bar, then select "Apps Script."
In the Apps Script editor, delete any existing code and replace it with the following code:

function findDuplicatesInColumn() {
  var sheet = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();
  var column = sheet.getRange('A:A').getValues(); // Replace 'A:A' with the range of your column
  var duplicates = [];

  for (var i = 0; i < column.length; i++) {
    var count = 0;
    for (var j = 0; j < column.length; j++) {
      if (column[i][0] == column[j][0]) {
        count++;
      }
    }
    if (count > 1 && duplicates.indexOf(column[i][0]) == -1) {
      duplicates.push(column[i][0]);
    }
  }

  return duplicates;
}

Save the script by clicking on the floppy disk icon or pressing Ctrl + S.
Close the Apps Script editor.
To use the custom function, select an empty cell in your sheet, then enter =findDuplicatesInColumn().

The custom function findDuplicatesInColumn() will search for duplicates in the specified column and return an array of the duplicate values. You can copy this formula across different cells or use it within other formulas as needed.

Use Case Examples

Finding duplicates in a column can be useful in various scenarios. Here are a few examples:

Data Cleansing: When dealing with large datasets, it's important to identify and remove duplicate entries to ensure accurate analysis and reporting.
Inventory Management: Duplicate product entries in an inventory list can lead to confusion and errors. Identifying and merging duplicates can help streamline inventory management processes.
Member Directory Validation: When maintaining a member directory, finding and eliminating duplicate names or contact information ensures accurate and up-to-date records.

In conclusion, by following the manual process using conditional formatting or using Google Apps Script, you can easily spot and handle duplicates within a column in Google Sheets. Whether you prefer manually identifying duplicates or automating the process, Google Sheets provides flexible options to suit your needs.

Here is a guide on how to highlight duplicates in Google Sheets, which might be helpful for you.
If you want to learn how to delete duplicates in Google Sheets, check out this tutorial.
To remove blank rows in Google Sheets, follow this guide for step-by-step instructions.
Sorting by column can be easily done in Google Sheets to organize your data effectively.
If you need to find duplicates in a column, this article provides a step-by-step guide to help you out.

Published 20 Jul 2023