In short: RowSlice splits one CSV into multiple files by the values in a column you choose: one file for each different value, up to 10,000 files in one run. Rows with an empty value go into blank.csv, and characters that are not allowed in file names are replaced with an underscore, so Lyon/Nord becomes Lyon_Nord.csv. Each file starts with the original header row, and every row is copied as it is, in its original order, so leading zeros and long ID numbers are not changed. The file is read a few megabytes at a time in your browser and is never uploaded.
How to Split a CSV by Column Value
- Choose or drag in your CSV file. The first rows are shown so you can check it was read correctly.
- Pick the column that holds the groups you want, for example Country, Sales rep or Order status.
- Press Split File. The progress bar shows how much of the file has been read so far and how fast it is going.
- Download everything as one ZIP, save all files into a folder (in Chrome and Edge), or download individual files from the list.
A Typical Example
Say you have a year of orders exported from your shop system, with a store column. Your managers each need only their own store's orders. Splitting by store produces files like this:
| Output file | Contains |
|---|---|
Berlin.csv | Header row + every order where store is Berlin |
Lyon.csv | Header row + every order where store is Lyon |
Paris.csv | Header row + every order where store is Paris |
blank.csv | Header row + orders with no store filled in |
Rows keep their original order inside each file, so a file sorted by date stays sorted by date.
When only one group matters — one store, one status, one month — filtering the CSV gives you that one file without writing a file for every other value in the column. When the file is simply too big for Excel or an upload limit and it does not matter which rows end up together, split a CSV into multiple files by row count or size instead. Split by column value when each group has to end up in a file of its own.
Why Not Just Use Excel Filters?
For a small file you can filter a column in Excel, copy the visible rows to a new sheet and save it, once per value. That breaks down quickly. With forty stores it is forty rounds of filter, copy, paste and save. And an Excel worksheet holds at most 1,048,576 rows, the limit Microsoft publishes, so a large export never loads whole: Excel stops at row 1,048,576 and warns that not all the data was loaded. To read an export that size before splitting it, open it in the CSV viewer, which pages through the file without a spreadsheet and without writing anything to your disk.
Excel also changes data when it opens a CSV. Postal codes like 00742 lose their leading zeros, long account numbers turn into 4.52E+15, and some codes are converted into dates. If you save the filtered rows back to CSV, those changes are saved too. RowSlice's split-by-column tool never interprets values: it copies the text of each row as it is.
How It Handles Large Files
Every row has to be read, but none has to be kept: the tool reads about 4 MB, writes those rows to their output files, and moves on. So a 40-store export becomes 40 files without the browser ever holding the whole export, and memory use stays within a fixed limit however large your file is.
Output files are written to your browser's private storage on your own disk rather than held in memory, and only a small number are open at any moment, so splitting into thousands of files works too. It correctly handles quoted values that contain commas or line breaks, files saved with semicolons or tabs, and files from older Windows programs that are not UTF-8, which come out as UTF-8.
Want to Split One Column into Several Instead?
Splitting by column value sorts whole rows into separate files; it does not break one column into two. If everything lands in column A when you open the CSV in Excel, the file usually uses a different separator from the one Excel expects: why a CSV opens in one column in Excel explains it, and the CSV converter can change the file's delimiter to commas, semicolons, tabs or pipes. To turn one value such as Austin, TX into a city column and a state column, use Data › Text to Columns in Excel.
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