CSV format and the error report
A CSV needs a url column (or destination, long_url). Optional columns: slug, title, tags (comma separated), notes. A plain list of URLs, one per line, works too.
Rules:
- Up to 5,000 rows per file; split larger exports.
- Slugs must be unique on the domain; a duplicate row is skipped and listed.
- Every destination is checked against Safe Browsing on import; flagged rows are skipped and listed.
The error report lists each skipped row with its line number and reason, so you can fix the file and import the rest.