How to Use — Step by Step
1
Upload Left file
Your primary table — the one whose rows drive the result.
2
Upload Right file
Your lookup table — like a VLOOKUP source.
3
Choose key column
A column shared by both files (e.g. Customer ID, Email, SKU).
4
Select join type
Inner · Left · Right · Outer — same as SQL JOIN modes.
5
Pick output columns
Tick exactly which columns from each file to keep.
6
Click Merge → Download
Preview the result table, then download the CSV.
Features
4 join modes
Inner, Left, Right and Outer.
Any key column
IDs, emails, product codes — any shared field.
Selective output
Keep only the columns you need.
Large file support
Handles tens of thousands of rows.
CSV & Excel input
Reads .csv, .xls, .xlsx files.
100% in-browser
Your data never leaves your device.
Export
Download format: Output: CSV with all selected columns from both files.
Privacy & Security
Your files never leave your device. All processing happens entirely inside your browser tab using JavaScript.
No data is uploaded to any server, no account is required, and nothing is stored after you close the tab.
Fully GDPR-friendly — no data processing obligations are created by using this tool.