Deduplicate rows in a CSV

How it works

Typically useful before an email campaign: you've merged two overlapping contact exports (for example a CRM export and an event registration list), and some rows end up duplicated. Paste or upload your combined CSV file, click "Deduplicate": strictly identical rows are detected and only the first occurrence of each is kept, avoiding sending the same email twice to the same person.

How are duplicates detected (exact row or just one column)?

The tool compares rows in their entirety: two rows are only considered duplicates if all of their columns are strictly identical. If your two exports contain the same email address but with a name spelled differently or an extra column, the rows won't be merged automatically — in that case you'll need to harmonize the columns before deduplicating.

Is the row order preserved?

Yes, the original row order is preserved: only later repeats of a row already seen are removed, and the first occurrence keeps its original position in the file.

Processing is entirely local, performed in your browser via WebAssembly: your list of contacts or emails never leaves your computer.