Android Factory Reset Protection

An Android system feature designed by Google to discourage theft of cellphones also discourages sale of used phones and perniciously motivates theft of Google passwords. The feature is sometimes called an “activation lock,” and modern cellphones will not operate without one.

An activation lock prevents someone else from gaining access to your phone should it be lost or stolen. If you're returning, replacing or selling your phone the lock should be disabled beforehand. If the activation lock is not removed from the phone it renders the phone unusable to anyone other than yourself.

Google and Samsung each have their own activation locks and offer different methods of removal. For Samsung phones, it is possible that both types of activation locks are present and you would need to remove both. Apple iPhones have similar protection that operates through iCloud accounts.

In most cases, a factory reset does not remove the activation lock from the phone. For example, if the phone is factory reset with the Google account still signed in, the phone will still ask for those credentials once it turns back on. Therefore it is safer for the account to be removed before the factory reset takes place to ensure your account is fully removed.

Note: If a Google account password is changed before performing the reset instead of being fully removed the message “Please sign in using one of the owners accounts for this device” will appear. This indicates the Google account on the phone is now locked for 72 hours and you must wait for it to reset.

See the article below for detailed information about the following techniques:

Removing your Google activation lock from device settings on your phone

Removing your Google activation lock online

Removing Samsung factory reset protection from your device

Removing your Android activation lock

When you change the password on your Google account, you might not be able to use the new password on another device for 24 hours (or 72 hours for older phones). This is done to prevent "suspicious" activity, like stealing someone's Google password and changing it, then logging into a device with the new password in order to harvest someone's personal data (banking information or other financial details like an Amazon account, specifically). You'll need to wait 24 hours after a password change before you can use the Google account to set up a device. If the device is still running Lollipop, that changes to 72 hours.”

What to do if you're locked out of your phone

How do I unlock my locked phone without my Google account?

The Apple ecology has a similar but subtly different method for this.

The activation lock on the iPhone home screen is by far Apple’s most popular and effective security feature. Known in earlier models as the Killswitch, the activation lock is a feature designed to prevent anyone from using your iPhone.The activation lock prevents your phone from being reactivated and also allows you to remotely erase your phone in case of theft. The activation lock works by linking your Apple ID with your device and requires a password when trying to reactivate or erase your device.While the activation lock can secure your device by protecting against unauthorized usage, it also presents challenges when transferring ownership of the device. If you’re planning to buy a used iPhone, the first thing you must verify is that the activation lock is turned off on the device. It’s easy to do this by verifying the iPhone’s IMEI number on iCloud. Before you sell your iPhone, make sure that your data has been erased and the activation lock has been turned off. Your personal data such as contacts, calendar and documents shouldn’t be deleted while you’re signed into iCloud with your Apple ID. Doing so will result in your data getting deleted from the iCloud servers.

How to Remove the Activation Lock for iPhones