Clean a Messy Spreadsheet of Text Without Losing Rows

Paste the messy column and ask for the transformation as a formula or a script, not a rewritten paste. That way you can audit it.

Tell Claude the exact rule: 'strip everything after the pipe,' or 'capitalize the first word only.' Vague asks get vague fixes.

Run it on five rows first. If those five are right, do the batch. If not, you've wasted five rows instead of five thousand.

The mistake is trusting the whole column at once. Spreadsheets don't forgive silent errors, and a wrong formula corrupts everything below it.