Switching or backing up your contacts should be safe and simple, but wrong formats often create problems during the upload process. This write-up explains you how to modify your VCF file so it works well with modern cloud contact systems. It explains how to clean your file removing duplicates and verifying text fields before trying to import VCF to iCloud. The steps help ensure that every phone number, email address, and name is recognized correctly by the destination. It also suggests checking small samples first, which can help you confirm that everything transfers exactly as expected before doing a full upload.

For more: https://www.convertertools.org/blog/convert-vcf-files-to-icloud-contacts/