If it’s ON: Telegram is actively (or has recently) uploaded your phone’s contact list to its servers to find Telegram users among them. Most of the contacts you see in your Telegram list who are also in your phone’s address book likely came from here.
If it’s OFF: Telegram is not currently syncing your phone’s address book. Any contacts you see are either from a previous sync (if you haven’t deleted them) or were added manually.
Checking Phone Permissions (if “Sync Contacts” isn’t working):
Android: Go to your phone’s Settings > Apps (or Apps & Notifications) > Telegram > Permissions > Contacts. Ensure “Contacts” permission is granted.
iOS: Go to your iPhone’s Settings app > scroll down to Telegram > Contacts. Ensure this toggle is ON.
If the app-level permission is off, Telegram cannot access your phone book, regardless of its in-app setting.
Telegram usually distinguishes telegram number database between contacts from your phone book and contacts added by username or from groups.
If they are in your phone’s contact list but not on Telegram, they will typically appear with an “Invite to Telegram” button next to their name.
Contacts Added Manually (by Username or from Groups):
If you added someone by their username! or if you initiated a chat with someone from a group and then added them as a Telegram contact! they might mobile numbers in logistics and e-commerce appear with the name you assigned them within Telegram (which belgium numbers could be different from your phone book).