Question 1

How do I merge multiple CSV files into one?

Accepted Answer

Add your CSV files by dragging them in or clicking the drop zone. Choose 'Stack rows' to combine them vertically (one after another) or 'Join by key' to merge side-by-side using a shared column. Click Merge and download the result.

Question 2

What happens if my CSV files have different headers?

Accepted Answer

In Stack mode with 'Union headers' enabled, all unique columns from every file are combined — missing values become empty. With the option off, rows are stacked as-is and only the first file's header is kept.

Question 3

Is my data uploaded to a server?

Accepted Answer

No. All merging happens entirely in your browser. Your CSV files are read locally and never sent anywhere.

Question 4

Can I merge CSVs with different delimiters?

Accepted Answer

Yes. Each file is auto-detected for its delimiter (comma, semicolon, tab or pipe). The merged output uses a single delimiter you choose.