There are two cases: (1) for normal LINE users and (2) for LINE@ (pronounced ‘line-at’) business users.

LINE Users
Let’s say your LINE ID is yourlineid. The link is

LINE@ Users
If your LINE@ ID is @yourlineatid, the link will be

On desktop browsers, clicking one of these links will take you to a page with a QR code associated with the LINE/LINE@ ID. Scan the QR code with LINE app to add the friend. On mobile, it will open up LINE app and ask if you want to add the friend.