This layer contains things that make up the IoT such as sensors, transducers, actuators, smartphones, smart devices, and Radio-Frequency Identification (RFID) tags. There can be many categories of sensors such as body sensors, home sensors, and environmental sensors based on the type of work they perform. This layer is the core of an IoT ecosystem where various sensors are used to sense real-world environments. This layer includes sensors that can monitor temperature, humidity, liquid flow, chemicals, air, pressure, and much more. Usually, an Analog to Digital Converter (ADC) is required on a device to turn the real-world analog signal into a digital signal that a microprocessor can understand.

Actuators in this layer provide the means to enable control of external environments, for example, starting a motor or opening a door. These components also require digital to analog converters to convert a digital signal into analog. This method is especially relevant when control of a mechanical component is required by the IoT device.