CSV joiner — merge two CSVs on a key
Join two CSV files on a shared column, like a database join. It runs entirely in your browser (0 uploads, works offline).
How to use it
- Paste the left and right CSVs.
- Set the join column and type.
- Copy or Download the joined CSV.
FAQ
How do I join two CSV files for free?
Paste both CSVs, name the shared column and pick inner or left join; this page matches rows by that key and combines the columns — on your device with no upload.
What is the difference between inner and left join?
Inner keeps only rows that match in both files; left keeps every row from the left file, filling blanks where the right has no match.
Is my data uploaded anywhere?
No. The join runs entirely in your browser and nothing is transmitted or stored, which you can verify by turning off your Wi-Fi.
Do the headers need to match?
Only the join column must exist in both files by the same name; the other columns are combined.
Limits
Joins two files on one key column; multi-key and outer joins are not included.
Related
The SQL playground does richer queries; the CSV cleaner tidies the inputs.
Bookmark this page (Ctrl+D, or ⌘D on Mac) or install the app — it works offline the next time you need it.