You may have noticed an option that says “Lock” whenever you tap and hold an individual text message from within some versions of the Android Messaging app. You might wonder what it does. You’re not the only one.
Locking a text message marks the message to prevent it from being deleted. There are still ways to delete locked text messages, the Lock feature just adds an extra layer of security to prevent accidental deletion.
So if you lock a text message, then later wish to delete the entire thread that message is included in, it will leave the locked messages and delete the rest. Some smartphones will prompt you to delete locked messages when deleting threads by providing an “Include protected message” or “Delete locked messages” check-box option.
If I factory reset my Android, will it retain locked messages?
No, it will not.