How to automatically remove duplicates from a list in Excel?
In Excel, we can use the Remove Duplicates feature to remove the same values from a list, but is there any trick to automatically remove duplicates from the list? In this article, I introduce the tricks on automatically removing duplicates if a duplicate appears in a specific Excel column.
Compare methods for automatically preventing duplicate entries
Auto remove duplicates from a list using Data Validation
Auto remove duplicates from a list using Kutools for Excel 
Compare methods for automatically preventing duplicate entries
Both methods below prevent new duplicate values from being entered into a specified range. They do not remove duplicates that already exist in the list. The main difference is whether you want to build the validation rule yourself or apply a ready-to-use duplicate restriction.
| Method | Best for | Setup | Result |
|---|---|---|---|
| Data Validation | Users who want a built-in Excel solution and control over the validation formula | Create a Custom rule with a COUNTIF formula | Blocks duplicate manual entries and displays a warning |
| Kutools for Excel | Quickly preventing duplicate entries without formulas | Select the range and apply Prevent Duplicate | Blocks duplicate entries and displays a warning automatically |
Auto remove duplicates from a list using Data Validation
1. Click Data > Data Validation. See screenshot:
2. In the popping dialog, under Settings tab, select Custom from the Allow list, and type the formula =COUNTIF($A$1:$A$20,A1)=1 into the Formula box. See screenshot:
In the formula, A1:A20 is the range in which you want to prevent duplicate entries.
3. Click OK. Now, if you type a duplicate value, a warning dialog will appear and the duplicate entry will be prevented.
Auto remove duplicates from a list using Kutools for Excel
If you are not familiar with formulas, you can apply Kutools for Excel’s Prevent Duplicate utility to stop duplicate values from being entered into a selected range without setting up a validation formula manually.
Select the range or column in which you want to prevent duplicate entries, and then click Kutools > Prevent Typing > Prevent Duplicate. See screenshot:
Some dialogs appear to remind you of certain notices. Click Yes > OK to close the dialogs.
Now, when you try to enter a value that already exists in the selected range, a warning dialog appears and prevents the duplicate entry.
Here is another related utility called Prevent Typing. You can specify characters that users are not allowed to enter, or define characters that are allowed in the selected range, as shown below:
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Demo: Auto Remove Duplicates Entries using Kutools for Excel
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