CSV Merge
Join two CSVs on a key column. Inner, left, right, or outer join — colliding column names get a configurable suffix on the right side.
About CSV Merge
CSV Merge joins two CSV files on a shared key column, supporting inner, left, right, and outer joins — the same join logic you'd write in SQL, but on flat files. When both sides have a column of the same name, you set a suffix so the right file's columns stay distinct. It runs entirely in your browser, so two private datasets can be combined without either being uploaded.
- Category
- edit
- Input
- Accepts: text/csv or text/plain.
- Output
- Outputs: text/csv (multiple).
- Cost
- Free, runs in your browser
- Memory
- low
Common uses
- Enrich an orders CSV with customer details by joining on customer ID (left join keeps every order)
- Find rows present in both files with an inner join on a shared key
- Combine two partial exports into one complete table with a full outer join
- Attach pricing from a product master file to a sales export on SKU
- Reconcile two systems by joining on an ID and inspecting which rows only appear on one side
Frequently asked questions
Which join types are supported?
Inner, left, right, and outer — matching standard SQL semantics. Inner keeps only matched keys; left and right keep all rows from one side; outer keeps everything.
What happens when both files have a column with the same name?
Colliding column names on the right file get a configurable suffix, so values from both sides survive without overwriting each other.
Is my data uploaded to merge it?
No. The join happens in your browser. Both CSVs stay on your device, which makes it safe for combining sensitive customer or financial tables.
What do I need to join on?
A key column that exists in both files. Rows are matched where the key values are equal, per the join type you choose.
What's the output?
A single merged CSV combining columns from both inputs, with the join applied and any name collisions suffixed.
Keywords
- csv
- merge
- join
- inner
- outer
- left
- combine