Which Android version introduced Smart Lock?

Android 5.0 introduced Smart Lock.

Released in 2014 under the dessert name Lollipop, Android 5.0 added Smart Lock as a way to reduce the friction of repeatedly entering a PIN, password, or pattern. The feature could keep a device unlocked when Android detected a trusted condition, such as a paired Bluetooth device, a trusted location, or an NFC tag.

Smart Lock was designed as a compromise between convenience and security. A user could keep a phone unlocked near a smartwatch or car system, for example, while still relying on a secure screen lock when the trusted condition disappeared. Later versions expanded and adjusted the available methods, including on-body detection and trusted faces on supported devices.

A common mix-up is confusing Smart Lock with Android’s later biometric-unlock features. Fingerprint support also became much more prominent around the Lollipop era, but fingerprint authentication is not the same feature. Smart Lock’s defining idea was conditional unlocking based on context or trusted devices.