How to Remove Duplicates from Spreadsheets and Lists

Duplicate entries waste time, skew analytics, and create confusion. When cleaning a customer email list or consolidating data from multiple sources, removing duplicates is a fundamental data hygiene task.

The Quick Answer

The fastest method depends on your data format:

• Text lists (emails, names): Use an online deduplication tool. Paste and clean in seconds
• Excel spreadsheets: Built-in “Remove Duplicates” feature (Data tab)
• Google Sheets: Data → Data cleanup → Remove duplicates
• Large datasets (10k+ rows): Excel Power Query or Python scripts

For simple lists under 10,000 entries, an online tool beats manual Excel work every time because there are no formulas and no confusion about which columns to check.

Methods Comparison

Method	Best For	Speed	Learning Curve	Preserves Formulas
Online Tool	Text lists, emails	Instant	None	N/A
Excel Remove Duplicates	Structured data	Fast	Easy	No
Google Sheets	Collaborative work	Fast	Easy	No
Excel UNIQUE() function	Dynamic ranges	Medium	Medium	Yes
Power Query	Repeating cleanup	Medium	Steep	Yes
Formulas (COUNTIF)	Learning exercise	Slow	Hard	Yes

The verdict: For one-off cleaning, use native tools. For recurring cleanup workflows, invest in Power Query or scripts.

Reference Chart: Method by Data Size

Rows	Recommended Method	Why
< 1,000	Online tool or native Excel/Sheets	Instant results, no setup
1,000 - 10,000	Excel Remove Duplicates	Fast, reliable
10,000 - 100,000	Excel Power Query	Handles large data efficiently
100,000+	Database (SQL) or Python/R	Spreadsheets slow down

Complexity matters too: If you need to check duplicates across multiple columns (e.g., first name + last name), native tools still win up to 50k rows.

Step-by-Step: Excel Remove Duplicates

Excel’s built-in feature is the gold standard for structured data.

Method 1: Remove Duplicates Tool

1. Select your data range (including headers)
2. Go to Data tab → Remove Duplicates (in Data Tools group)
3. Excel auto-selects all columns; uncheck any you want to ignore
   • Example: To find people with same email regardless of name, check only “Email” column
4. Click OK
5. Excel shows a summary: “X duplicate values found and removed; Y unique values remain”

What happens: Excel keeps the first occurrence and deletes subsequent duplicates. This is usually what you want.

Method 2: Advanced Filter (More Control)

1. Data tab → Advanced (in Sort & Filter group)
2. Select Copy to another location
3. Check Unique records only
4. Choose where to output the clean list
5. Click OK

Advantage: Original data stays untouched because clean data goes to a new range.

Method 3: UNIQUE() Function (Microsoft 365)

If you have Microsoft 365, use the dynamic UNIQUE() function:

=UNIQUE(A2:A100)

This creates a live list that updates when source data changes, making it perfect for dashboards.

Step-by-Step: Google Sheets

Google Sheets has two approaches.

Method 1: Built-in Tool (Easiest)

1. Select your data range (including headers)
2. Data menu → Data cleanup → Remove duplicates
3. Check which columns to compare (default: all columns)
4. Check “Data has header row” if applicable
5. Click Remove duplicates

Google Sheets highlights removed rows before deleting, giving you a chance to review.

Method 2: UNIQUE() Function

Google Sheets has had UNIQUE() longer than Excel:

=UNIQUE(A2:A100)

Pro tip: Combine with SORT() for alphabetized output:

=SORT(UNIQUE(A2:A100))

Pro Tips

1. Preserve the First Occurrence (Not Random)

Both Excel and Sheets keep the first occurrence they encounter. This matters when duplicates have different metadata:

Email	Sign-up Date	Status
jane@example.com	2023-01-15	Active
jane@example.com	2024-06-10	Inactive

If you remove duplicates by email, you’ll keep the 2023 entry. Solution: Sort by the most important column first (e.g., newest date), then deduplicate.

2. Case Sensitivity

• Excel Remove Duplicates: Case-insensitive (treats “John” and “john” as duplicates)
• Google Sheets: Case-insensitive by default
• UNIQUE() function: Case-insensitive in both platforms
• Online tools: Most are case-insensitive, but check settings

If you need case-sensitive deduplication, you’ll need a formula or script.

3. Trim Whitespace First

Invisible spaces break duplicate detection:

"john@example.com"   ← Looks identical
"john@example.com "  ← Trailing space = different

Fix in Excel: Select column, then Data, Text to Columns, and Finish (trims automatically)

Fix in Google Sheets: =TRIM(A2) or Data → Data cleanup → Trim whitespace

4. Check Multiple Columns

For customer databases, check across first name + last name + email:

1. Excel Remove Duplicates: Check all three columns
2. Google Sheets: Select all three columns before running tool
3. Online tool: Concatenate first: =A2&B2&C2, deduplicate, then split back

5. Keep Duplicates for Review

Before deleting, flag them:

Excel formula:

=COUNTIF($A$2:A2,A2)>1

Drag down. This marks all duplicates with TRUE while keeping the first occurrence unmarked, so you can filter and review before deleting.

Common Mistakes

1. Losing Data Because You Didn’t Copy First

Mistake: Running Remove Duplicates on your only copy of the data.

Fix: Always duplicate your sheet first (right-click tab → Duplicate). Or use Advanced Filter’s “Copy to another location” option.

2. Checking the Wrong Column

Mistake: You want to remove duplicate emails but check all columns, so “John Smith, john@example.com” and “John Q. Smith, john@example.com” are treated as different.

Fix: Only check the email column in the Remove Duplicates dialog.

3. Partial Duplicates (Different Formatting)

Mistake: Excel treats these as different:

• 555-1234 vs (555) 1234
• January 15, 2024 vs 1/15/2024

Fix: Standardize formatting first. Use TEXT() for dates, remove punctuation from phone numbers with SUBSTITUTE().

4. Ignoring Hidden Rows

Mistake: Excel’s Remove Duplicates tool includes hidden rows. If you filtered to show only active customers, hidden inactive customers still get processed.

Fix: Apply your filter, and then copy visible cells to a new range before deduplicating.

5. Not Checking Sort Order First

Mistake: You want to keep the newest entry but your data is sorted oldest-first.

Fix: Sort descending by date before running Remove Duplicates.

6. Thinking “Unique” Means “Distinct Count”

Mistake: Using UNIQUE() when you actually need to count how many times each value appears.

Fix: For frequency counts, use a Pivot Table (Insert → PivotTable → Count of values).

When Online Tools Are Better

Use an online duplicate remover when you have:

• Email lists from multiple sources (copy/paste from forms, exports, etc.)
• Plain text lists (no complex columns)
• Quick one-off cleanup (faster than opening Excel)
• No spreadsheet access (working from a tablet or borrowed computer)

Privacy note: Don’t paste sensitive data (SSNs, medical records) into online tools. For confidential data, use offline Excel/Sheets.

Advanced: Power Query for Recurring Cleanup

If you import the same messy data weekly (e.g., CRM exports), Power Query automates the entire workflow:

1. Data tab → Get Data → From File
2. Power Query Editor opens
3. Home tab → Remove Rows → Remove Duplicates
4. Click Close & Load

The magic: Next week, just click Refresh and the same cleanup steps run automatically.

Frequently Asked Questions

Q: Does Excel’s Remove Duplicates feature keep the first or last occurrence?

Excel keeps the first occurrence it encounters and deletes all subsequent duplicates. This matters when duplicates have different metadata. For example, if “jane@example.com” appears twice with different sign-up dates, you’ll keep whichever row appears first in your current sort order. To control which record to keep, sort your data by the most important column (like newest date) before running Remove Duplicates.

Q: Will removing duplicates delete my original data permanently?

Yes, Excel’s Remove Duplicates tool modifies your data in place and can’t be undone after saving the file. Always duplicate your sheet first (right-click tab → Duplicate) or use the Advanced Filter method with “Copy to another location” selected, which preserves your original data. For Google Sheets, the tool highlights duplicates before deletion, giving you a chance to review, but it’s still permanent once confirmed.

Q: How do I remove duplicates based on multiple columns instead of just one?

In Excel’s Remove Duplicates dialog, check all the columns you want to compare together. For example, to find people with the same first name AND last name AND email, check all three columns. Excel treats a row as duplicate only if all checked columns match. In Google Sheets, select all relevant columns before going to Data → Data cleanup → Remove duplicates, then check which columns to include in the comparison.

Q: Are duplicate detection tools case-sensitive or case-insensitive?

Both Excel and Google Sheets treat duplicates as case-insensitive by default, meaning “John” and “john” are considered duplicates. The UNIQUE() function in both platforms is also case-insensitive. Most online duplicate removers are case-insensitive, but check the tool’s settings if case sensitivity matters for your data. If you need case-sensitive deduplication, you’ll need to use custom formulas or scripts.

Q: Why are some duplicates not being detected even though they look identical?

The most common culprits are invisible whitespace (trailing spaces, tabs, line breaks), different formatting that looks the same (phone numbers like “555-1234” vs “(555) 1234”), or hidden characters copied from websites or PDFs. Run “Trim whitespace” (Google Sheets: Data → Data cleanup → Trim whitespace) or use =TRIM() formulas before deduplicating. For dates and numbers, standardize formatting using TEXT() or SUBSTITUTE() functions first.

Use Our Tool for Instant Cleanup

Skip the spreadsheet entirely for simple lists. Our duplicate remover tool handles:

• Line-by-line text (email lists, usernames)
• Comma-separated values
• Case-sensitive or insensitive options
• Instant preview before downloading

Perfect for cleaning up email lists, contest entries, or survey responses in under 10 seconds.