Merge CSV Files Online
How do you combine CSV files? Drop two or more CSV files below, arrange the order, and click Merge. You get one combined file with a single header row, and mismatched columns are aligned automatically. Free, no signup, fully private.
Drop CSV files here or click to browse (select multiple)
Processed locally — never uploaded
How to merge CSV files (step by step)
- Add your files. Drag and drop multiple CSVs at once, or click the box to select them. Add more at any time.
- Arrange the order. Use the up/down arrows to set which file's rows come first. Remove a file with ✕.
- Click "Merge CSV files". Headers are unified automatically; missing values become empty cells.
- Download the result. One clean CSV with a single header row.
Why use this CSV merger?
- Handles mismatched columns: the output contains the union of all headers.
- Order control: reorder files before merging.
- Private: merging happens on your device, never on a server.
- Free and unlimited: no signup, no file count or size limits.
Frequently asked questions
How do I merge multiple CSV files into one?
Drop two or more CSV files into the tool above, arrange them in the order you want, and click Merge. A single combined CSV downloads instantly. Everything runs in your browser with no upload.
What happens if my CSV files have different columns?
The merger builds the union of all columns automatically. Rows from files that lack a column simply get an empty value there, so no data is lost.
Do duplicate header rows get repeated in the merged file?
No. Each file is parsed with its own header and the output contains exactly one header row at the top.
How many files can I merge at once?
There is no fixed limit on the number of files. Practical limits depend on your device memory, but merging dozens of files totalling hundreds of megabytes works fine.
Is my data uploaded to a server?
No. Files are combined locally in your browser using a background worker. Nothing is transmitted anywhere.