How to find duplicate value in Google Sheets

How to highlight cell if value duplicate in same column for google spreadsheet?

Step - 01: Select the whole column (your desired column)

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Step - 02: Click on Format menu

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Step - 03: Click Conditional formatting sub-menu

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Step - 04: Click on Format cells if... dropdown button

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Step - 05: Click on Custom formula is

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Step - 06: Click on Value or formula text box

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Step - 07: Type this =countif(A:A,A1)>1 formula in the Value or formula text box

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Step - 08: Click on Formatting style dropdown button or leave it Default

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Step - 09: Click on Fill Color icon

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Step - 10: Click on your desired color for highlight duplicate value in your sheets

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Step - 11: Now Click on Done button.

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[N. B.: Ensure the range applies to your column e.g. A1:A100.
Now anything you write in the A1:A100 cells will be checked and if there is found any duplicate value then it will be coloured. For multiple columns, use countifs.]

I hope this article will help you in your work.
Thank you!