If your Apple Device is ever lost or stolen, the Activation Lock function prevents anybody else from using it. When you enable Find My on your iPhone, Activation Lock is activated immediately. Activation Lock keeps your device safe, even if it falls into the wrong hands, and can help you reclaim it. Even if you remotely wipe your device, Activation Lock can prevent someone from reactivating it without your consent.
All you must do is keep Find My Phone on and remember your Apple ID and password.
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Here’s how Activation Lock on iPhone works
When an iPhone, iPad, iPod touch, Apple Watch, or Mac computer with an Apple T2 security chip or Apple silicon is activated or recovered, the device contacts Apple to see if Activation Lock is enabled.
When you enable Find My, Activation Lock is activated automatically. Once activated, Apple securely keeps your Apple ID on its activation servers and associates it with your device. Before anybody can turn off Find My, wipe your device, or reactivate and use your device, they must first enter your Apple ID password or device passcode.
How to check if the Activation Lock iPhone feature is turned on
To check for Activation Lock on an iPhone, go to Settings, and hit your Apple ID.
In Apple ID Settings, click “Find My.”
Look for the “Find My iPhone” section under “Find My” settings. If it shows “On,” Activation Lock is enabled. If it shows “Off,” then Activation Lock is turned off.
To turn it on, go to “Find My iPhone” and toggle the switch next to “Find My iPhone” to the off position. If you intend to sell or give away your iPhone, you must also sign out of iCloud. After which, you conduct a factory reset before handing it along.
After the factory reset completes, you’ll know that Activation Lock is truly disabled if you see the “Hello” screen inviting you to set up your iPhone. If you’re buying a used iPhone and it’s been factory-reset, make sure it shows you the standard “Hello” setup screen after powering it on! Otherwise, if the iPhone prompts you for an Apple ID and password to proceed with setup, it is still locked to the original owner. The owner can log in and disable “Find My iPhone”. He might also login to their Apple ID through the Apple website and remotely delete the iPhone from their list of devices.