How to identify duplicates in column

Answer

To identify duplicates in a column in Excel, you can use several methods depending on whether you want to highlight, filter, or flag the duplicates.

Method 1: Using Conditional Formatting

Conditional Formatting highlights duplicates visually.

1. Select the column where you want to identify duplicates.

2. Go to the Home tab on the ribbon.

3. Click Conditional Formatting → Highlight Cells Rules → Duplicate Values.

4. In the dialog box, choose a formatting style (e.g., red fill with dark red text).

5. Click OK.

Duplicates in the column are now highlighted with the chosen formatting. Unique values remain unchanged.

Windows vs. Mac: The steps are the same. Only the Home tab layout might look slightly different on Mac.

Method 2: Using a Formula with COUNTIF

You can create a new column to flag duplicates with COUNTIF.

1. Suppose your data is in column A, starting from A2.

2. In cell B2, enter the formula: 

   =IF(COUNTIF(A:A, A2)>1, "Duplicate", "Unique")

3. Press Enter and drag the formula down the column.

• "Duplicate" appears for repeated values.

• "Unique" appears for values that occur only once.

This method is useful when you need a clear textual indicator of duplicates.

Method 3: Using the Remove Duplicates Tool (For Identification and Removal)

1. Select the column.

2. Go to the Data tab.

3. Click Remove Duplicates.

4. In the dialog box, ensure only the column you want is checked.

5. Click OK.

Excel will display a message showing how many duplicates were removed and how many unique values remain. This method identifies duplicates while removing them.

Method 4: Using a Filter to Display Duplicates

1. Select the column with data.

2. Go to the Data tab → click Filter.

3. Click the filter arrow in the column header.

4. Choose Filter by Color if duplicates are highlighted using Conditional Formatting, or use a custom filter with COUNTIF flags.

This shows only the duplicates while hiding unique values.

Notes

• Conditional Formatting and COUNTIF methods do not remove data; they only identify duplicates.

• COUNTIF method is dynamic: if new duplicates appear, the formula updates automatically.

• Remove Duplicates tool is permanent and cannot automatically adjust to new duplicates.

You can choose a method depending on whether you want visual identification, flagging, or removal.

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