You are not thinking about putting your phone back to factory settings later. A profile about you on your phone will disappear. If you really think so, you're dead wrong!
I believe that most people now have a habit when changing mobile phones. After buying a new mobile phone, the old mobile phone is sold directly to the recycled mobile phone! For the sake of safety, some friends will restore the phone to factory settings in advance and then sell it to others. But do you think that's safe? In fact, this operation does not have any effect! Because the phone factory reset is just a restore of the system files. Some user data has been deleted. However, the data on the phone's internal memory chip has not been completely deleted.
It simply "marks" the storage space in the area where the deleted data is located so that it can be overwritten. But the original data is still there. It can still be restored by technical means!
You want to completely cover this part of the area. The only way to do this is to rewrite the new data!
For example, after the phone has been restored to factory settings. Then re-download some videos or files. It's important to note here that re-downloading isn't something that can be done with a little bit of it. You need to fill up all the memory! Of course, at this time, do not save any personal information and important data on the mobile phone. Otherwise it's still a futile job! Finally, the phone memory is full and then restore the factory settings. That way, even if he can restore the data in his phone. That's some useless data too! You don't have to worry about your personal information being leaked! Do you understand?