Does each output file keep the header?

Yes. Every chunk is written with the original header row at the top followed by its share of the data rows, so each file is a complete, valid CSV on its own.

How does split-by-column-value work?

The tool reads the chosen column, groups all rows that share the same value, and writes one file per distinct value. File names are derived from the value with unsafe characters replaced, for example EU rows go to EU.csv.

What happens to the remainder when splitting by row count?

The last file simply contains whatever rows are left over. If you ask for 100 rows per file and have 250 rows, you get files of 100, 100, and 50 rows.

No. The CSV is parsed and split entirely in your browser, and each download is generated locally with a Blob. Nothing is sent to a server.

CSV Splitter — Gera Tools

Split a big CSV into manageable files

The CSV Splitter breaks one large CSV into several smaller ones. Split by a fixed number of rows per file to create even batches for upload limits or processing windows, or split by a column value to produce one file per region, category, customer, or any other grouping key. Every output keeps the header row.

How it works

The CSV is parsed with a quote-aware reader so commas and newlines inside quoted fields stay intact. In row-count mode the data rows are sliced into consecutive groups of the size you choose, and each group is written out with the header on top — the final group holds any remainder.

In column-value mode the tool reads your chosen column for every row, groups rows that share the same value while preserving first-seen order, and writes one file per distinct value. The value becomes the file name, with any characters that are not letters, digits, dot, underscore, or hyphen replaced so the name is safe to save.

Tips and notes

Use row-count splitting when a downstream system caps file size or row count — for example an import that rejects files over a certain number of records. Use column-value splitting to fan a dataset out by a natural partition such as country or month. Each chunk is independently valid, so you can re-open, re-import, or re-join any of them without reconstructing the header.