WhatsApp's contact synchronization is a two-way process. Both you and the person you want to connect with need to have each other's phone numbers stored in your respective address books to establish a connection. WhatsApp does not provide a unilateral method for adding contacts who do not have your number stored in their address book.

Here's how it works:

1. Mutual Contact: For you to see someone's WhatsApp profile and initiate a chat, both of you must have each other's phone numbers saved in your phone's address book. This mutual connection is a security and privacy measure to ensure that you are connecting with people you know.

2. Privacy and Control: WhatsApp prioritizes user privacy and control over their contact list. By requiring mutual contacts, WhatsApp allows users to decide who can contact them and view their information.

3. No One-Sided Adding: WhatsApp does not offer a feature that allows you to add someone to your contact list without their consent or without them adding your number to their contacts.

4. Invite to WhatsApp: You can invite someone to WhatsApp by sending them an invitation link or message through other means, such as SMS or email. However, they will still need to save your number in their address book to establish a connection.

In summary, WhatsApp's contact synchronization is designed to be a mutual process to protect user privacy and ensure that both parties consent to the connection. You cannot unilaterally add someone to your WhatsApp contact list if they have not saved your number in their phone's address book. If you want to connect with someone on WhatsApp, it's best to ask them to save your number in their contacts, and once that's done, you can initiate a chat with them on the platform.