What is this CSV merge tool?
A free, browser-based tool to append multiple CSV files into one. Upload several CSVs and their rows are stacked into a single file, with columns aligned by header name rather than position. Choose union to keep every column across all files, or intersection to keep only the columns shared by every file. It's perfect for combining exports split across multiple files. Everything runs locally in your browser, so your data is never uploaded.
How to use it
- Upload the CSV files you want to combine on the left.
- Choose how to align columns: union (keep all) or intersection (shared only).
- Review the combined CSV in the output box.
- Copy the result or download the merged CSV.
Common use cases
- Combining monthly exports into a single yearly CSV.
- Merging lead lists from multiple sources into one file.
- Stacking files with slightly different columns using union mode.