PoppyOSRemove duplicate rows from a CSV file, without uploading it anywhere
Pick the columns that define a duplicate, and get a clean CSV plus a second CSV that lists every removed row, its original row number and why it went. One HTML file that runs in your browser, works with no internet connection, and is yours to keep.
Why people use it
Nothing disappears silently
Besides the clean file you get a "removed rows" file with the original row number and the reason: duplicate of row N, wrong number of columns, or empty match column.
Your file stays on your computer
The page is technically blocked from using the network, so customer, patient and order files never leave your machine. No account, no upload, works offline.
You decide what a duplicate is
Match on one or more columns, such as Email, or on the whole row. Ignore upper and lower case and stray spaces. Keep the first copy or the last.
Formula protection
Values starting with =, +, - or @ get a leading apostrophe so a spreadsheet reads them as text (why this matters). Tested in LibreOffice Calc 26.8 with formula evaluation on; not yet tested in Microsoft Excel.
How it compares with the free options
| Option | Good for | What it lacks |
|---|---|---|
| Excel or Google Sheets "Remove duplicates" | quick one-off clean-ups | no record of what was removed (workaround); stray spaces hide duplicates |
| Free "remove duplicates" websites | no install, free | some upload your file and it is hard to tell which; they need the internet |
| Command line or Python | programmers, automation | needs code (example) |
| Offline CSV Cleaner | private files, and a record of what changed | does not open .xlsx (save as CSV first); does not guess that two different spellings are the same person |
Details
- Tested in Chrome 155, Firefox 157 and WebKit 27.2 (the engine behind Safari; Safari itself not tested), with byte-identical results.
- In our tests, a 100,000-row file was cleaned in 0.2 to 0.3 seconds in each of those browsers.
- Handles quoted commas, line breaks inside cells, semicolon, tab and pipe separators, and byte-order marks.
- Included: the HTML file, a README, a sample file, the licence and SHA-256 checksums for every file.
- One-time price. Personal licence: one person, any number of their own devices. Organisation licence: up to three named people. 14-day refund for any reason.
- How it was made: the cleaning engine was built with AI-assisted tools and is tested automatically against an independent reference implementation on hundreds of tricky files.
- It removes duplicates inside one file. To compare two files, see Offline CSV Compare.
Get it: USD 15, one-time Try the free demo first
The demo uses the same cleaning engine. It cleans and downloads files up to 200 rows; for larger files it shows how many duplicates it found so you can see the result before you buy.