A CRM's bulk import capping at ten thousand rows, an email platform rejecting anything over a certain file size, these limits are common enough that splitting a large CSV is really about getting each piece under a platform's actual limit, not handling big data in the abstract, and a naive split by line count that leaves the header row only in the first chunk breaks every import after that one. This tool splits a large CSV into smaller files, repeating the header row at the top of every chunk so each piece imports correctly on its own. Useful for splitting a massive contact export into pieces that each fit under a bulk import tool's row limit, breaking up a large CSV so every file still opens correctly with its own header row, or preparing smaller files from one large export for a platform with a strict file size cap.