They can — but only if they’re built for contact conversion, not generic file handling. Large XLSX files usually fail because of inconsistent formats, empty cells, or mixed data types. Premium tools account for this by validating records during processing. A dedicated Excel to vCard solution like Softaken Excel to vCard Converter is designed to process thousands of contacts while maintaining field integrity. Names stay segmented, phone numbers retain labels, and addresses remain structured. That’s the difference between a successful bulk import and hours of cleanup after syncing to phones or email clients.