WhatsApp can find which of your contacts are using WhatsApp quickly and easily. WhatsApp reads your contacts' phone numbers from your phone's address book and automatically adds them to WhatsApp.

If you would like WhatsApp to recognize new contacts that use WhatsApp, simply enter their name and number into your Windows Phone address book.

When you are adding contacts, make sure that you enter their phone number in the full international format:

• + [Country Code] [Full Phone Number].
• Be sure to omit any leading 0's from the phone number.
• For a detailed explanation on how to add international contacts, read this article.

Adding an unknown number

If someone who is not saved in your address book sends you an initial message in WhatsApp, you will have the option to save their contact information by tapping add to contacts.

Alternatively, if you are chatting with an unsaved contact and want to save their number, follow these steps:

1. Open the chat with the unsaved contact.
2. Tap More
3. Choose add to contacts.

Learn how to add contacts on: Android | iPhone