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Removing duplicates from multiple columns means Excel identifies rows where the selected columns contain identical values and deletes every repeated row, leaving the first unique instance in place. To remove duplicates from multiple columns in Excel:

1. Select the entire data range that contains the columns.

2. Go to Data on the Ribbon.

3. Select Remove Duplicates in the Data Tools group.

4. Choose the specific columns that Excel must check.

5. Select OK to confirm the removal.

Excel evaluates the selected columns as a single combined key. A row is flagged as a duplicate when all checked columns match another row exactly. Excel removes all but the earliest matching row.

Windows vs. Mac differences

Windows:

1. The Data tab places Remove Duplicates in the center of the Ribbon.

2. Keyboard shortcut: Alt + A + M navigates to Remove Duplicates.

Mac:

1. The Data tab places Remove Duplicates in the Data Tools section with identical iconography.

2. No dedicated shortcut sequence exists through the Control or Command modifiers for direct access. Manual selection through the Ribbon is required.

How to remove duplicates across all columns at once

To remove duplicates across all columns at once:

1. Select the full table.

2. Select Data > Remove Duplicates.

3. Keep every column checked.

4. Select OK.

Excel removes rows where every column matches another row.

How to remove duplicates based on a subset of columns

To remove duplicates based on only two or three specific columns:

1. Highlight the table.

2. Select Remove Duplicates.

3. Uncheck the columns you want Excel to ignore.

4. Select OK.

Excel checks only the selected columns. Unique values in unchecked columns do not protect a row from deletion.

How to keep the original data while removing duplicates

To keep the original data:

1. Copy the range.

2. Paste it into a new location.

3. Run the Remove Duplicates command on the copied version.

This method preserves the source dataset.

How to remove duplicates using Advanced Filter

Advanced Filter creates a unique list without deleting the source data.

1. Select the columns for filtering.

2. Go to Data > Advanced.

3. Choose Copy to another location.

4. Check Unique records only.

5. Provide a destination range.

6. Confirm by selecting OK.

Advanced Filter keeps one representative row for every unique combination.

How to remove duplicates with formulas (without deleting data)

Formulas do not delete duplicates. Formulas identify unique and repeated records so you can filter or extract them.

Step-by-step:

1. Insert a helper column.

2. Enter a formula such as COUNTIFS to identify duplicate patterns.

3. Filter the helper column.

4. Delete or extract results as needed.

Users normally choose:  

=COUNTIFS(A:A, A2, B:B, B2)

Removing duplicates is possible after filtering values with a count greater than 1.

How uniqueness changes with data size

Excel removes duplicates with consistent speed for ranges up to 100,000 rows. Performance shifts after 500,000 rows, where processing time grows by around 30% to 40%. Filtering before using Remove Duplicates reduces the time cost.

How Excel identifies duplicates internally

Excel treats each selected column as part of a composite key. Excel compares:

1. Data type.

2. Text string match.

3. Case-insensitive characters.

4. Numeric values.

5. Date serial numbers.

Excel removes any row where the combination repeats an earlier record.

How to avoid accidental data loss

To avoid data loss:

1. Create a backup sheet.

2. Validate column selections before confirming.

3. Sort the dataset before removing duplicates when priority retention matters.

Sorting gives control over which row stays because Excel keeps the first matching row.

How to remove duplicates while keeping the last row

Excel always preserves the first appearance. To keep the last occurrence:

1. Sort the dataset so the newest row appears first.

2. Run Remove Duplicates.

3. Excel keeps the first row in the sorted order.

Sorting reverses the retention order.

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