Full International Format: This is crucial, especially for international contacts. Always save numbers with the full international dialing code, including the plus sign (+).
Example: For a number in Bangladesh, it should be +88017XXXXXXXX (not just 017XXXXXXXX). For the US, +12125551234.
Consistency: Ensure numbers are saved consistently. Avoid mixing dashes, spaces, or parentheses if possible.
Save to the Correct Account: If you use multiple accounts (e.g., Google, iCloud, device-only), ensure your contacts are saved to an account that is syncing with your phone and that WhatsApp has access to.
3. Refresh WhatsApp Contacts:
After adding new contacts to your phone's address book, WhatsApp usually picks them up automatically. If not, you can force a refresh.
How to Refresh:
Open WhatsApp.
Go to the Chats tab.
Tap the New Chat icon (usually a whatsapp number list green circle with a speech bubble or pencil icon, often in the bottom right).
On Android: Tap the three vertical dots (Menu) in the top right corner.
On iPhone: (This step is often not needed as iOS refreshes contacts more automatically. You'll simply see new contacts appear if they are on WhatsApp).
Select "Refresh".
4. Sync Your Phone's Contacts with Cloud Accounts (e.g., Google Contacts, iCloud):
This is the best way to ensure your contacts are backed up and seamlessly available across devices, which helps WhatsApp sync.
Google Contacts (Android):
Go to your phone's Settings > Accounts (or "Users & Accounts").
Tap "Account sync" (or "Sync account").
Make sure "Contacts" is toggled ON. You can often tap the three dots and select "Sync now" to force a sync.