- Back up all your data; because once it's gone, it's gone. There's no undo button you can press.
- Next, plug the charger into the device so it's getting power for the deletion process. This is important because the process can take hours.
- Go to Settings > Security > Encrypt phone (or Encrypt tablet) to begin the process on Android 4.4 or lower, or go Settings > Security > Screen lock to begin the process on Android 5.0 and higher (this is unnecessary on new devices running Android 6.0 Marshmallow).
- You will be guided through the process. Set a strong password. Don't bother encrypting the SD card because you can pop this out and keep it rather than wipe it. This process can take over an hour, so be patient and make sure you have the time.
- Go to Settings > Backup & reset > Factory data reset and then tap Reset phone (orReset tablet).
- Once this process is complete your data is gone. Technically, it's still written there on the flash memory in what is now reported as free space, and will eventually be overwritten. Because it's encrypted recovering it would be difficult. However, if you want to completely eradicate it, jump to the next step.
- The best way to get rid of the encrypted data is to overwrite it with new data. There are two ways you can do this. You can load some big files onto the device (big video files are ideal for this) until the storage is full up and then delete these files.
Step 1: Set up Android to PC Transfer and connect your phone to PC
Step 2: Select files to backup to computer
Under My devices, there are 6 types of data that you can delete from your android phone, including Apps, SMS, Contacts, Media (audio & video), Photo.
To delete contents:
Take wiping SMS as example, click SMS and you will see the detail info on the right panel, then select conversation by checking checkbox. Tag on Delete button . After few seconds, all of selected data will be deleted on your computer.