How to remove duplicates in Excel and CSV files (step by step)

The three families of duplicates

Repeated rows are not all alike, and the removal method depends on the type of duplicate.

• Strict duplicate: two rows identical cell by cell. Removal is safe, keep one row.
• Functional duplicate by email: the same address appears with different spellings (upper case, trailing spaces). Normalise first, then deduplicate.
• Duplicate by ID: the same customer code, SKU or EAN appears on several rows with diverging values. Here you merge (upsert) instead of deleting blindly.

Why Excel's Remove Duplicates is not enough

Excel compares values exactly as displayed. "marc.durand@gmail.com" and "MARC.DURAND@GMAIL.COM" count as two different values, and so does an address followed by an invisible space. Real duplicates slip through.

Second limitation: Excel deletes the row without telling you what it held. If the second row carried a phone number missing from the first, that data is gone for good.

The reliable four-step method

To truly deduplicate a file, the order of operations matters more than the tool.

• 1. Trim leading and trailing spaces on every text column.
• 2. Lowercase all emails and standardise phone formats.
• 3. Detect strict duplicates, then duplicates by email and by ID.
• 4. Review the final sheet before export and check how many rows were removed.

How Import Cleaner handles duplicates

Import Cleaner runs that sequence automatically in your browser: the file is parsed, columns are mapped to target fields, then 26 checks run, including strict duplicates, duplicate emails and repeated identifiers.

Every affected row is highlighted in an interactive grid: you see the kept row, the discarded row and the reason. Apply the fix in one click or decide row by row, then export a clean CSV or Excel file.

FAQ

How do I remove duplicates from a CSV without Excel?

Load the file into Import Cleaner: the CSV is parsed in the browser, duplicates are listed, and you export a clean file with no software to install.

Is my data uploaded to a server?

No. Parsing, detection and fixing all run locally in your browser; no file leaves your device.

Can I deduplicate on a single column?

Yes. After column mapping, deduplication can use the email or the identifier rather than the whole row.

How do I remove duplicates in Excel without losing data?

Compare both rows before deleting: the grid shows the kept and the discarded row, so a phone number that only exists in the duplicate is not lost.

How do I find near-duplicates that are not identical?

Normalise case, spaces and phone formats first: most near-identical rows then become strict duplicates that are detected automatically.

Does it work on large CSV files?

Yes, large files are processed in batches in the browser, with an alert when the file exceeds the usual Excel limits.