About contact upload
Contact upload is an optional feature that allows us to check which of your contacts in your device's address book are also WhatsApp users. It also means we can update your WhatsApp contact list when your contacts who aren't using WhatsApp yet sign up later. We care about your privacy and don't share your contact list with Meta.
When you use contact upload and grant WhatsApp access to your device address book, WhatsApp will access and upload the phone numbers in your address book on a regular basis, including those of WhatsApp users and your other contacts. We don’t collect any of the other information that could appear in your device address book including names, email addresses, etc.
If any of your contacts aren’t yet using WhatsApp, we protect their privacy by managing the phone number in a way that is designed to prevent those contacts from being identified by WhatsApp. We do this by creating a cryptographic hash value of their phone number, and then delete the number. The hash value enables us to more efficiently connect you with these contacts when they join WhatsApp.
Separately, we also create a cryptographic hash representation of the phone numbers in your device address book which we use to detect and combat misuse of contact upload.
You can control the contact upload feature from your device-based settings.Read more about how to use WhatsApp responsibly in our Help Center article.