The German telecom portal Teletarv.de stressed the need to delete personal data from your smartphone or tablet before selling or offering it to others, as the SIM card and memory card are removed at the beginning and all user accounts such as Google account are deleted.
Because the user may be unable to reliably remove data from the phone’s memory, German experts recommend that the memory be encrypted so that the subsequent user of the smartphone has difficulty accessing the stored data.
The encryption function can be found in Google Android from version 4 onwards in the Settings menu under “Security”. For new versions of Android, the encryption function is effective by default, and nothing is required.
In the next step, the phone must be returned to factory settings, and this option is located on Android devices under the “Backup and Reset” or “Reset Options” clause. Mobile devices with an “IOS” system are in the settings menu under “General” and “Reset”.