Merge CSV Files Learn more

Append two large CSV files into one. Handles massive files (100MB+) that crash Excel or Google Sheets. Streamed locally in your browser - nothing is uploaded.

Select two CSV files to merge
File 1 (primary) - header kept from this file
File 2 (append) - first row skipped by default
Merging... 0%
Merge Complete
0
Total Rows
0
Output Size
0
Time (sec)
0
Header Rows Skipped
Files are processed in streaming chunks - even 500MB+ CSVs work smoothly. Nothing leaves your browser.
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