Prepare phone numbers for a Klaviyo CSV import
Phone data is easy to export in a human-readable form that is awkward for bulk import. The important distinction is formatting versus missing information.
Country information matters
Klaviyo requires phone numbers to include a country code or to have country information supplied separately. ReadyRows does not invent a country when it is missing.
Safe normalization
ReadyRows can remove presentation punctuation and normalize obvious international forms such as a leading 00 into +. It preserves the underlying digits rather than trying to infer a different number.
Blocked versus review
If the number has an implausible digit count or lacks country context, ReadyRows marks the row as blocking. Duplicate phone numbers are warnings because automatically deleting one could lose legitimate profile data.
Official reference
Klaviyo lists country information and accepted phone formatting as requirements in its invalid format troubleshooting guide.
Check the file before you re-import it
ReadyRows scans CSV and XLSX files locally, separates blocking rows and generates an import-ready CSV plus a mapping guide.
Open the free fixerReadyRows is an independent tool and is not affiliated with Klaviyo. Product rules can change; for account-specific decisions, confirm the latest guidance in Klaviyo's Help Center.