CSV Data Deduplicator
Remove duplicate rows from a CSV file in seconds. Compare all columns or only the ones you name (for example email), optionally ignoring upper/lower case and extra spaces, and keep the first or last occurrence. You see how many rows were removed and which ones, and can download the clean file – or just the duplicates for review.
- Runs in your browser
- No sign-up
- Free to use
Processed entirely in your browser – your data is not uploaded. Files up to 50 MB.
How to use CSV Data Deduplicator
- Paste CSV or open a file.
- Name the columns to compare (optional).
- Choose the options.
- Download the deduplicated CSV.
CSV Data Deduplicator features
Column-based
Compare by any columns.
Fuzzy basics
Ignore case and extra spaces.
Keep first or last
Choose which row survives.
Duplicates export
Review before deleting.
Separator kept
Output uses the input separator.
Private
Runs in your browser; nothing is uploaded.
When to use CSV Data Deduplicator
- Cleaning mailing lists.
- Merging CRM exports.
- Preparing product imports.
- Removing repeated log lines.
CSV Data Deduplicator FAQ
Is the header row compared?
No, the first row is treated as the header.
Does the order change?
No, rows keep their original order.
What about near-duplicates?
Trimming and case-folding catch common variations; spelling differences are not merged.
Can it merge duplicate rows instead of deleting them?
No. It keeps one row per duplicate group. Merge information from duplicates first if both rows contain different useful values.
Does it change the order of rows?
No. Rows keep their original order; only the duplicates are removed.
Which delimiters are supported?
Comma, semicolon, tab and pipe, detected automatically. Quoted fields with line breaks are handled.
Can I deduplicate by two columns together?
Yes. Name both columns, for example first name and date of birth, and rows count as duplicates only when both match.
Count once
Duplicate rows inflate counts, send the same email twice and break unique keys on import.
Duplicates often differ only slightly – “Anna@Example.com ” and “anna@example.com” are the same customer. Comparing selected columns such as email, with case and extra spaces ignored, finds those, while comparing all columns finds only exact copies of a row.
Keeping the first occurrence preserves the oldest record; keeping the last keeps the most recent update, which is better when rows were appended over time. The list of removed rows lets you check the result before you replace your original file.
Everything happens in your browser, so customer lists and exports never leave your device. Keep a copy of the original until you are sure the right rows were removed.
Typical uses are cleaning mailing lists before a send, merging customer exports from two systems and preparing data for import into a CRM. Deduplicating on an email or customer ID column usually catches more real duplicates than comparing whole rows, because other columns – dates, notes, formatting – often differ slightly.