What is this CSV join tool?
A free, browser-based tool to join two CSV files on a shared key column — like a database JOIN or a spreadsheet VLOOKUP. Choose an inner join to keep only rows that match in both files, or a left join to keep every row from the first file and leave the right-side columns empty where there is no match. Output columns default to every column from both files, with the duplicate key column dropped. Everything runs locally in your browser, so your data is never uploaded.
How to use it
- Upload or paste your two CSV files (CSV A and CSV B) on the left.
- Pick the key column in each file — the column whose values link the two.
- Choose an inner join or a left join.
- Review the joined CSV, then copy it or download the file.
Common use cases
- Enriching a lead list by joining it with a company details file on email or ID.
- Matching order data with customer data on a shared customer ID.
- Adding metrics from one export to a master list using a left join.