Before you start
What you need
A valid CSV and, optionally, exact header names used as the duplicate key.
Developer & Data
CSV Duplicate Finder
Find repeated CSV records by selected columns and keep their original source-row numbers.
- 01Runs in this browser
- 02Limits are explicit
- 03Copy or download output
No black box
How this tool handles the input
Rows are grouped by the exact text in the selected columns. Only groups with more than one row are returned, with group and source-row metadata.
What you get
What the page gives back
A CSV containing all repeated rows, duplicate group numbers, and original row numbers.
Keep in mind
Use the result responsibly
Matching is exact and case-sensitive. Similar spelling, whitespace, phone formats, and normalized emails are not inferred.
Practical uses
Where this tool earns its place
- Find repeated email addresses before an import.
- Review duplicate invoice references.
- Isolate exact repeated records for cleanup.
Verified data boundary
Source text stays on this page.
The published contract marks these tools as client-only processing. Nirmion uses the API only to confirm that this workspace is enabled in MySQL; source values and results are not sent to Flask.