A CSV that is too large to import, email or open comfortably needs to be broken up. Maybe an upload form caps you at a few thousand rows, or you want to hand each region its own slice of a report. Splitting by hand means counting rows and copying carefully; doing it in one step is faster and avoids off-by-one mistakes.
The short version: add your CSV, choose to split by a row count or by a column, and download the parts. The split CSV tool runs on your device, so nothing is uploaded.
Two ways to split, for two different reasons
There are two questions that lead people to split a file, and each has its own mode.
The first is about size. You need each piece small enough to fit a limit, and you do not care which rows go where. That is split by row count: set how many rows per file, and the data is chopped into evenly sized parts in order.
The second is about grouping. You want all the rows for each category together, in their own file. That is split by a column: pick a column, and every distinct value in it becomes one file. A sales export split on Region gives you one file per region, with all of that region’s rows inside.
Why the header matters
The detail that trips people up when splitting by hand is the header row. If you cut a file at row 2,000 and the second half has no column names at the top, half your parts will not import cleanly, because the receiving tool has no idea what the columns mean.
When the first row of your file holds column names, that header is carried into the top of every part automatically. Each piece reads as a complete, self-contained CSV.
How to split a CSV
Step 1: Add the file
Drop a .csv file into the tool, or paste the text in directly. Confirm whether the first row is a header so it can be repeated correctly.
Step 2: Choose how to split
For evenly sized pieces, choose “by row count” and set the rows per file. To group rows, choose “by a column” and pick the column to group on.
Step 3: Download the parts
Each part is listed with its row count. Download them one at a time, or all at once. The files are named so they sort in order.
A note on the opposite job
If you reach a point where you have too many small files and want them back together, the merge CSV tool recombines them, lining up columns by name. And if you only need certain columns from a file rather than certain rows, extracting columns is the tool for that.