Drop in two or more CSV files and get one file back. Columns are matched by their heading rather than by their position, which is the difference that matters: two exports of the same data often list the same fields in a different order, and a tool that stacks them by position writes the email addresses into the phone column without complaining. Fields missing from one file are left empty rather than shifting the row along.
This page loads no libraries at all — the work is done by the browser itself. Your file is read on your own machine and never sent anywhere — open your browser's network tab and watch while you use it.
They still line up, because matching is done on the heading text. This is the single reason to use a tool rather than pasting the files together: two exports of the same table frequently differ in column order, and stacking them by position silently writes each value into the wrong field. The result looks perfectly well-formed, which is why nobody catches it until much later.
The column is kept and left empty for the rows that do not have it. You are also told, in the summary, which files were missing which columns — so a field that only exists in half your data is something you find out now rather than after a report comes out wrong.
Yes. Files are appended in the order you selected them, and rows keep their order within each file. Nothing is sorted or reshuffled.
No, deliberately. Merging and deduplicating are separate decisions and combining them hides one inside the other. Run the duplicate remover afterwards if you want that, and you will see exactly how many rows it dropped.
Everything here is free and works the same way — in your browser.