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EXCEL · PRACTICAL GUIDE

Highlight Duplicates in Excel

Use conditional formatting to make repeated keys visible.

Practice EXCELLearning path

What this solves

Spot duplicate invoice numbers or HU labels. This pattern is useful when the business question is clear but a generic tutorial is too abstract.

The rule

Create a formula rule based on COUNTIF.

=COUNTIF($A:$A,A2)>1
Google Sheets: The core pattern is also usable in Google Sheets; exact function support and locale separators can differ.

Real-work checklist

  1. Define the business key and expected grain before writing the formula, query or markup.
  2. Test the pattern on a small known sample where you can verify the answer manually.
  3. Check missing values, duplicates and data types before trusting a large result.
  4. Scale to the real file or database only after the logic is proven.

Common mistake

Visual highlighting does not remove duplicates and does not define which row should be kept.

Try it next

PracticeChange the example and verify the result.Use a toolMove from a small example to real work.Related contentFind guides, errors and scenarios on this topic.