Merge CSV Files
Free tool to merge CSV files into one. Matches columns by header name, adds a source file column and removes duplicate rows. Private — runs in your browser.
- No upload — 100% private
- Instant, on your device
- Free, no sign-up
- Works offline once loaded
How it works
How to use Merge CSV Files
Drop two or more CSV files onto the page (you can keep adding more), or try the sample files.
Choose All columns, Common columns or First file’s columns, and reorder or untick columns in the list.
Optionally add a source file name column and remove duplicate rows.
Check the preview, then download the merged CSV.
Why use it
Why use our Merge CSV Files tool
Matches columns by name
Columns are aligned by header, not position — files with columns in a different order or with extra columns merge correctly.
Loose header matching
“Email”, “ email ” and “EMAIL” are treated as the same column, so exports from different systems line up.
You choose the columns
Keep every column, only the ones all files share, or the first file’s layout — then reorder or drop columns before downloading.
Source column and de-duplication
Add a column with each row’s original file name, and drop rows that appear in more than one file.
Mixed delimiters
Comma, semicolon, tab and pipe files are detected one by one, so a European Excel export merges with a US one.
Private and fast
Files are combined in a background worker on your device and never uploaded, even when they are tens of megabytes.
FAQ
Frequently asked questions
How do I merge multiple CSV files into one?
Drop all the files here at once (or add them one by one). They are combined in the order shown, with one header row at the top, and you can download the result as merged.csv.
What if my CSV files have different columns?
Columns are matched by header name. With All columns, the merged file contains every column from every file and cells are left empty where a file doesn’t have that column. Common columns keeps only the columns every file has.
Can I see which file each row came from?
Yes. Tick Add source file name column and a column (called source_file by default — you can rename it) is added at the start with each row’s file name.
How are duplicate rows removed?
With Remove duplicate rows on, a row is dropped when every merged column matches a row that came earlier. The source file column is ignored when comparing, so the same record in two files is kept only once.
Do the files need the same delimiter?
No. Each file’s delimiter is detected automatically, and you pick the delimiter for the merged output — comma by default.
Are my files uploaded?
No. Merging happens entirely in your browser. Your CSV files never leave your device.
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