How it works
The CSV is parsed character by character — not split by line first — so a quoted field containing a comma or a newline is not mistaken for extra columns or extra rows. Each cell is then trimmed and re-quoted only where quoting is actually needed.
Why column count matters
A row with more or fewer columns than the header usually means a stray comma inside an unquoted value, or a row that got cut off partway through. This is a common, silent cause of data ending up in the wrong column when a spreadsheet or script reads the file.
What this does not fix
This validates structure, not content — it will not catch a value that is in the right column but has the wrong type or format for what that column is supposed to hold.