When you’d split a CSV
The usual trigger is size. An Excel worksheet stops at 1,048,576 rows, so a bigger CSV is silently truncated when you open it — every row past the limit just disappears. Even below that, a multi-hundred-megabyte file can be painfully slow to open. Other times a system only accepts uploads up to a certain row count or file size, so you need the data in even chunks. Splitting solves both: each part is small enough to open or upload, and because every row lands in exactly one part, nothing is lost.
By rows, or into a set number of files
Two ways to divide it, depending on what the other end needs:
| Option | What it does | Good for |
|---|---|---|
| By rows per file | Each part has up to the row count you set (plus the header) | A hard per-file row/size limit downstream |
| Into N files | The data is divided into that many roughly-equal parts | Sharing the work into a fixed number of pieces |
Either way, the header row is copied to the top of every part, so each file opens with the right column names and imports cleanly on its own. Download them all in a single zip, or grab any one part on its own.
If you have several CSVs to join back into one, use the merger; and if a part still won’t open cleanly in Excel, the repair tools fix the usual damage.
Open the CSV merger →What it does and doesn’t do
The splitter divides by row position, not by meaning. It doesn’t group rows by a column value (all of one customer together, say) — it simply cuts the file into sequential blocks with the header repeated. That’s exactly what you want for “make this openable” or “chunk it for upload,” but if you need to split by category, that’s a filtering job, not this. Everything runs in your browser, so even a very large file is processed on your own machine and never uploaded.
Related
Combining files instead of splitting them? See the CSV merger and the guide on merging multiple CSV files. Splitting because Excel mangled the file? Fix that first with the repair tools, or read opening a CSV in Excel without breaking it. If Excel refused the file outright or showed only part of it, read what to do when a CSV is too big for Excel — it covers the 1,048,576-row ceiling and how to tell whether rows were silently dropped. Browse all guides.
Frequently asked questions
How do I split a large CSV file into smaller ones?
Drop the file into the splitter above, choose a maximum number of rows per file or a number of files to split into, and click Split. Each part keeps the header, and you can download them all in one zip or individually. It runs in your browser, so even a large file is never uploaded.
Why won’t my CSV open fully in Excel?
Excel worksheets stop at 1,048,576 rows, so a bigger CSV is truncated on open and you silently lose every row past the limit. Very large files can also be slow or impossible to open. Splitting into parts under the limit lets you open each one, and nothing is lost because every row ends up in exactly one part.
Does each split file keep the header row?
Yes. The first row is treated as a header and copied to the top of every part, so each file is independently usable. If your file has no header, untick First row is a header and the rows are split without repeating the first line.
Is my file uploaded when I split it?
No. The splitter reads the file with the browser’s own FileReader and creates the parts locally in JavaScript. The file never leaves your device, and the zip is assembled in the browser too.