Facebook has recently updated its policy in Help center page and clarified users needs to have Facebook account to sign up for Facebook messenger.
Earlier this update, Facebook allows the users to sign up for messenger without Facebook account by using phone number only. With this, users have enjoying the chat functionality without Facebook account.
Now, Facebook has revoked this option of using messenger without Facebook account. Here is the updated of its policy from their Help center page.
Facebook spokesperson stated a email to VentureBeat saying “We found that the vast majority of people who use Messenger already log in through Facebook and we want to simplify the process. If you already use Messenger without a Facebook account, no need to do anything”. Its clearly stating that users who were already using messenger without Facebook account need not to do anything,this policy is applicable for upcoming users only.