Built in rechargeable Li-ion Battery.No longer to change batteries frequently.Separate ON/OFF switch and Smart auto sleep feature design for power saving. Bluetooth connection Save USB Port. Just turn it on, push “connect” button and then select “Bluetooth Keyboard” in the Bluetooth settings of your device pairing the bluetooth keyboard. Universal Compatibility and easy to set. Widely Compatible with Android Windows iOS. Works on Computer, Desktop, PC, Laptop, Apple iPad iPhone, Galaxy Tab, Surface pro & More. The keyboard is Not fully compatible with Mac System.