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 we don't share your contact list with Meta Platforms Inc. or other Meta Companies for their own use, even when they provide us with services.
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 typically daily, but this depends on various factors including how often a user uses WhatsApp, 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. Each cryptographic hash value is stored on WhatsApp’s servers, linked to the WhatsApp users who uploaded the corresponding phone numbers before they were hashed so that we can 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. For example, we assess the hashes to determine whether there have been unusual changes in the address book. This does not involve tracking or comparing individual phone numbers.
You can control the contact upload feature from your device-based settings. If you choose not to use Contact Upload you can still communicate with people who have WhatsApp but certain functionality will be limited.
Read more about how to use WhatsApp responsibly in our Help Center article.