Remove duplicate rows from a CSV or Excel file
A duplicate row rarely looks identical twice — one copy is in lowercase, one has a trailing space, one has the name spaced differently. DataMadeClean normalizes casing and whitespace first, then removes what's left over as an exact match, so duplicates hiding behind formatting differences don't slip through.
No account needed · CSV and XLSX · keeps the first occurrence
Why duplicate rows are hard to spot by eye
Formatting differences can hide matches until the relevant fields have been normalised.
- The same row entered twice with different capitalization — "Priya Nair" and "priya nair"
- A trailing space or extra internal space that makes two otherwise identical rows look different to a plain string comparison
- Rows repeated across merged exports or re-imported lists
- A spreadsheet's own "Remove Duplicates" tool checking the whole row, so one differing column keeps an otherwise duplicate row
Before / after
The same three rows, one customer
Before
| Name | |
|---|---|
| Priya Nair | priya@lumen.co |
| priya nair | priya@lumen.co |
| Priya Nair | PRIYA@LUMEN.CO |
After
| Name | |
|---|---|
| Priya Nair | priya@lumen.co |
| duplicate — removed | |
| duplicate — removed | |
Casing and whitespace are normalized first — that's what turns three differently-formatted rows into three identical ones, so the duplicate check can actually catch them. Only one row survives.
How DataMadeClean handles it
Upload, normalize, deduplicate
Upload your file
CSV or XLSX — no account needed to try it.
Normalize first
Casing and whitespace are cleaned up before duplicates are compared, so formatting differences don't hide a match.
Remove duplicates
Rows that are now identical are reduced to one — the first occurrence is kept.
Review & download
See exactly how many rows were removed and which ones, then download the cleaned file.
Your file is only ever used to clean it. An anonymous upload and its result are deleted an hour after cleaning; signed in, results follow your account's retention setting.
Limitations
What exact-match deduplication won't catch
- Two genuinely different people who happen to share a name and a shared inbox aren't flagged — DataMadeClean removes matching rows, not matching people.
- A typo that makes two rows for the same person look different — "Priya Nair" vs "Priya Nair " with an unrelated typo elsewhere in the row — won't be merged unless the differing value is one DataMadeClean already normalizes.
Review the recorded duplicate removals before downloading the cleaned file.
Try a CSV free →Questions
How duplicate detection works
What counts as a duplicate row?
A row whose values match an earlier row across every column, compared after whitespace and casing have been normalized. A row that differs in even one column — a different signup date, say — is left alone, because it is not the same record.
Will it catch duplicates with different casing or extra spaces?
Yes, and that is the point of normalizing first. “Priya Nair”, “priya nair” with a double space, and “PRIYA NAIR” all reduce to the same row, which an exact-match check in a spreadsheet would miss entirely.
Which of the duplicates is kept?
The first one in the file. The rows removed after it are each listed in the summary, so you can see how many went and where they were.
Can it find near-duplicates that are not identical?
Pro checks can flag similar names sharing an email address or phone number for review. They do not automatically merge contacts or delete near-matching rows. Exact duplicate row removal is included on every plan.
Does it work on Excel files as well as CSV?
Yes. An .xlsx workbook is read directly and returned as .xlsx, with no conversion to CSV in between.
How long is my file kept?
Anonymous uploads and their results are deleted an hour after cleaning. Signed in, results follow your account's retention period, seven days by default, and you can shorten it or delete a result yourself at any time. Read the privacy policy.
Upload your file and see which rows are duplicates.
No signup required.
Clean a file free →Get in touch if you have a question first.