FAQ
CSV Tools FAQ
Find answers about splitting, merging, converting, and transforming CSV files, organized by tool.
Basic tools
Questions by tool
Split a CSV by column value
What happens to rows with a blank split value?
Put them in a separate CSV or exclude them. Excluded rows appear in the summary.
Does splitting change my original CSV?
No. New CSV files and a ZIP are created in your browser.
Questions by tool
Merge CSV files vertically
How many times is the header written?
Only the first file's header is written; later files add data rows.
Can I merge files with different encodings?
Yes. Each file is detected and converted to the output encoding you choose.
Questions by tool
Convert CSV encoding or save as JSON
Can I create a UTF-8 CSV for Excel?
Yes. UTF-8 CSV output includes a BOM.
Does conversion rewrite my CSV values?
Encoding conversion preserves values. Typed JSON columns change type; blanks remain empty strings.
Questions by tool
Join two CSV files by key
What happens to unmatched right-side fields in a LEFT JOIN?
The left row remains and the unmatched right-side fields are blank.
How is this different from merging vertically?
A key join adds columns; a vertical merge appends rows.
Transform and organize
Questions by tool
Filter CSV rows by a condition
Can I apply several conditions at once?
The current tool supports one column and one condition. Filter the result again if needed.
Are uppercase and lowercase letters treated differently?
Use the case-sensitive option. When off, uppercase and lowercase match.
Questions by tool
Select and reorder CSV columns
Can I rename columns here?
No. Header text is preserved from the source CSV.
Does changing the selection modify my original file?
No. A new CSV containing the selected columns is created.
Questions by tool
Remove duplicate CSV rows
Which row is kept when duplicates are found?
The first occurrence is kept; later rows with the same key are excluded.
Can a duplicate key use several columns?
Yes. Select multiple columns for the duplicate key.
Questions by tool
Sort CSV rows by multiple columns
Can I sort dates?
Yes, when text order matches date order, as with ISO dates.
Can I change the priority of several sort columns?
Yes. Move keys up or down; the top key is compared first.
Aggregate
Questions by tool
Group and aggregate CSV rows
What is the difference between row count and non-empty count?
Row count includes all rows; non-empty count includes rows with a value in the selected column.
Are the original detail rows included in the output?
No. Keep the source CSV if you need the detail rows.