splittools

Split a large CSV into multiple files

cut locally · nothing uploaded

about this tool

The split.tools CSV splitter breaks a large CSV, TSV or delimited text file into smaller files — by a fixed number of rows, into a set number of equal files, or into parts that stay under a size limit. The header row is copied to the top of every part, so each file opens and imports on its own.

It is built for the files other tools choke on. Excel stops at 1,048,576 rows, Google Sheets at 10 million cells, and most online splitters at a few hundred megabytes of upload. Here the file is read from your disk in 8 MB slices and the parts are references into the original, so a multi-gigabyte export splits without being loaded into memory or sent anywhere.

Splitting happens on raw bytes, never on decoded text. Line breaks inside quoted fields stay inside their row (RFC 4180), CRLF or LF endings and a UTF-8 BOM are preserved exactly, and accented characters can't be mangled by a re-encode — because nothing is re-encoded.

under the blade

Split modes
Rows per file · number of files (equal rows) · max MB per file
Header
Detected from row 1 and repeated in every part (toggle off for headerless data)
Multi-line cells
Quote-aware: a line break inside "…" doesn't end the row
Encodings
UTF-8 (with or without BOM), ASCII, Windows-1252/Latin-1 — passed through byte for byte
Line endings
CRLF, LF and classic-Mac CR all recognised and preserved
File size
No cap; read in 8 MB slices. ZIP download up to 4 GB, individual parts beyond
Output names
name_part001.csv, name_part002.csv … zero-padded so they sort correctly
Privacy
Runs in the browser tab; works offline once loaded

how it works

  1. 1 cm

    Drop your CSV on the mat

    The file is scanned locally: row count, line-ending style, encoding and delimiter appear in seconds, with the first rows shown exactly as stored.

  2. 2 cm

    Choose how to cut

    Set rows per file (one click for Excel's limit), a number of equal files, or a maximum size in MB. Keep the header option on to repeat row 1 in every part.

  3. 3 cm

    Split and download

    Press Split CSV, check the part list with each file's row count and size, then download the set as one ZIP or pick parts individually.

frequently asked questions

How do I open a CSV that's too large for Excel?

Excel shows at most 1,048,576 rows per sheet, including the header. Choose 'Rows per file' and click the 'Excel max' preset (1,048,575 data rows); each part then opens fully in Excel with its own header row.

Does every split file keep the header row?

Yes, as long as 'First row is a header' is ticked. The header bytes are copied verbatim to the top of each part. Untick it for headerless data so row 1 is treated as data.

Will cells that contain line breaks get cut in half?

No. In a CSV, a line break inside a double-quoted field belongs to that cell. The splitter tracks quote state byte by byte and only cuts at line breaks outside quotes. If your data has unmatched quotes (like 12" pipe), the tool warns you and you can switch quote tracking off.

Is my CSV uploaded anywhere?

No. The file is read directly from your disk by your browser and the parts are assembled in the tab. Customer lists, transaction exports and other sensitive data never leave your machine — you can confirm it in the network inspector or by going offline.

Why are accented characters broken when I open a part in Excel?

Excel guesses the encoding of a CSV and only reliably detects UTF-8 when the file starts with a byte-order mark (BOM). If your source has one, keep 'Copy the UTF-8 BOM into every part' ticked so each part opens correctly.

Can I split a semicolon- or tab-separated file?

Yes. Splitting by rows only depends on line breaks and quotes, never on the delimiter, so comma, semicolon, tab and pipe files all split identically. The detected delimiter is shown for reference.

How big a file can it handle?

There is no imposed limit. The file is streamed in 8 MB slices and parts are assembled as references into the original file, so memory use stays low even for multi-gigabyte exports. ZIP downloads are capped at 4 GB total; beyond that, download parts individually.