Yes, completely free with no signup required.

Does my data leave my device?

No. All merging happens locally in your browser — no data is sent to a server.

Does it work on mobile?

Yes. The tool is mobile-first and works on any modern browser.

Paste two or more CSV blocks below and merge them into a single file with deduplicated headers.

100% in your browser. Your file never leaves your device.

CSV block 1

CSV block 2

Paste CSV block 1 above, fill in block 2 below, then click Merge CSVs.

Paste your first CSV block (including the header row) into CSV block 1.
Paste your second CSV block into CSV block 2.
Click "Merge CSVs" — the tool deduplicates the header and stacks all data rows, then click "Download merged.csv".

Is this tool free?: Yes, completely free with no signup required.
Does my data leave my device?: No. All merging happens locally in your browser — no data is sent to a server.
Does it work on mobile?: Yes. The tool is mobile-first and works on any modern browser.