Fix “invalid list format” before a Klaviyo import
Klaviyo List properties expect array-shaped data. Values that look natural in a spreadsheet—such as comma-separated tags—can still be the wrong type for the destination property.
Why this error happens
A Klaviyo property mapped as a List should contain a JSON array, for example ["VIP","Wholesale"]. Plain comma-separated text such as VIP, Wholesale is not the same data type.
What ReadyRows checks
ReadyRows samples custom columns, identifies columns that look like List properties and flags non-empty values that are not valid JSON arrays. It does not guess how an ambiguous text value should be split.
Safe next step
Review the flagged column, confirm that the destination property really is a List, and convert only values whose intended items are unambiguous. If the property is actually Text, map it as Text instead.
Official reference
Klaviyo documents the relevant import rule in its invalid format troubleshooting guide.
Check the file before you re-import it
ReadyRows scans the file locally in your browser, highlights platform-specific import risks and separates rows that need attention from rows that are ready to export.
Open the free Klaviyo fixerReadyRows is an independent tool and is not affiliated with Klaviyo. Import rules can change; confirm account-specific behavior in the platform's official documentation.