iCloud Lock (officially Apple Activation Lock) is a security feature that ties an iPhone, iPad, Mac, Apple Watch, or AirPods to the original owner's Apple ID. After a factory reset, the device cannot be activated without the original Apple ID and password.
The lock is server-side, Apple verifies activation against its central servers each time the device boots after reset. There is no legitimate bypass on current iOS, iPadOS, or macOS versions. Tools and services advertising “iCloud unlock” are almost universally fraudulent or short-lived exploits patched within weeks.
For wholesale buyers, iCloud Lock status is the single highest-impact verification check. An iCloud-locked iPhone trades at parts value (typically 10-15 percent of clean equivalent) because it cannot be reused as a working device. Mixing iCloud-locked units into a Grade A or B lot is one of the most common fraud patterns in the secondary market.
Verify by powering on a sample after factory reset; the Activation Lock screen will appear within seconds if the lock is engaged. Apple GSX (for authorised service providers) and Swappa's ESN check are the standard pre-purchase verification routes.