Merge CSV Files Online
Combine multiple CSV files into one unified master dataset.
Add CSV Files to Merge
Select two or more CSV files from your computer
Private by Design — Your CSV Stays on Your Device
OnlineCSV processes your files entirely client-side using browser JavaScript. Your CSV contents are never uploaded to any server, database, or remote service.
No account requiredWorks offlineZero data transmission
How to Use Merge CSV Files
1
Upload Multiple CSVs
Drag and drop 2 or more CSV files into the merger zone.
2
Choose Merge Strategy
Select Append Rows (same structure) or Union Columns (differing columns).
3
Download Merged CSV
Download the combined single CSV file.
Frequently Asked Questions
What happens if files have different column headers?
In Union Columns mode, missing column cells are left blank without losing data from any file.