You have a folder of CSV exports that belong together, one per month or one per region, and you need them in a single file. Opening each in turn and copying rows by hand is slow and easy to get wrong. The faster way is to merge them and let the columns line up automatically.
The short version: drop your CSV files in, choose how columns should align, and download one combined CSV. The merge CSV tool does this on your device, so nothing is uploaded.
The catch with merging CSVs: the columns rarely match
A CSV is just rows of text, so stacking two files sounds trivial. The trouble starts when the files were not exported the same way. One has an Email column, another calls it email address. One file gained a Notes column halfway through the year. Paste them together blindly and your data ends up under the wrong headings.
That is why matching matters more than the stacking itself. The goal is for every value to land under the right column name, even when the files disagree about which columns exist and in what order.
Three ways to line columns up
You get three modes, and the right one depends on how tidy your files are.
| Mode | Use it when |
|---|---|
| Keep all columns | Files share most columns but not all. Every column name is kept and missing cells go blank. |
| First file’s columns | The first file defines the shape you want, and extra columns in later files are noise to drop. |
| By position | Files have no headers, or you want a raw stack lined up by column order. |
“Keep all columns” is the safe default. It reads the header of every file, builds the full set of column names, and places each row’s values under the matching headers. A file missing one of those columns simply leaves that cell empty, so you never lose data and never shift a value into the wrong column.
How to merge your files
Step 1: Add the CSV files
Drop two or more .csv files into the tool. They are listed in the order you add them, which is also the order their rows appear in the result.
Step 2: Choose how columns align
Pick “keep all columns” unless you have a reason not to. If your files have no header row, switch to position mode so columns line up by their slot rather than by a name that is not there.
Step 3: Download the combined CSV
The preview shows the merged table so you can confirm the columns look right. Download a single CSV with every row, ready to import or analyse.
After merging: a couple of common follow-ups
Two things often come up once files are combined. If the same record appears in more than one source file, you will have duplicate rows; the duplicate-row remover clears those, matching on the whole row or just a key column like an email. And if the merged file is now too big for an import limit, you can split it back into evenly sized pieces.
Want to merge whole Excel workbooks rather than CSVs, keeping each as its own sheet? Use the merge Excel tool instead.