Binary sensor

Binary sensors are similar to other sensors in that they monitor the states and conditions of different entities. Where binary sensors differ is they can only return one of two mutually exclusive values. For example, a binary sensor for a window may report a value of open or closed, a switch on or off, a condition true or false.

This either/or constraint is what makes these sensors binary. They are digital in nature, whereas analog sensors, like temperature and weight sensors, return a range of values.

Some binary sensors are created automatically when you add a device integration. For example, adding the ecobee integration will create a binary sensor to detect room occupancy. Other binary sensors can be created manually using the template integration or using an input boolean helper.

The state of binary sensor

A binary sensor can have two states: on or off. However, in the frontend, they might not be called on or off, but use an alternative term to be more meaningful in context. For example, hot/cold, locked/unlocked. The meaning of an on or off state depends on the device class.

In addition, the entity can have the following states:

• Unavailable: The entity is currently unavailable.
• Unknown: The state is not yet known.

Device class

A device class is a measurement categorization in Home Assistant. It influences how the entity is represented in the dashboard. This can be modified in the customize section. For example, different states may be represented by different icons, colors, or text.

The screenshot shows a few examples of different device classes for binary sensors:

Example of various device classes icons in on and off state. The on image in this example has state_color: true specified in the entities card configuration to receive the icon coloring.

The following device classes are supported for binary sensors:

• None: Generic on/off. This is the default and doesn’t need to be set.
• battery: on means low, off means normal
• battery_charging: on means charging, off means not charging
• carbon_monoxide: on means carbon monoxide detected, off no carbon monoxide (clear)
• cold: on means cold, off means normal
• connectivity: on means connected, off means disconnected
• door: on means open, off means closed
• garage_door: on means open, off means closed
• gas: on means gas detected, off means no gas (clear)
• heat: on means hot, off means normal
• light: on means light detected, off means no light
• lock: on means open (unlocked), off means closed (locked)
• moisture: on means moisture detected (wet), off means no moisture (dry)
• motion: on means motion detected, off means no motion (clear)
• moving: on means moving, off means not moving (stopped)
• occupancy: on means occupied (detected), off means not occupied (clear)
• opening: on means open, off means closed
• plug: on means device is plugged in, off means device is unplugged
• power: on means power detected, off means no power
• presence: on means home, off means away
• problem: on means problem detected, off means no problem (OK)
• running: on means running, off means not running
• safety: on means unsafe, off means safe
• smoke: on means smoke detected, off means no smoke (clear)
• sound: on means sound detected, off means no sound (clear)
• tamper: on means tampering detected, off means no tampering (clear)
• update: on means update available, off means up-to-date
• vibration: on means vibration detected, off means no vibration (clear)
• window: on means open, off means closed

For comparison, here are the device classes for analog sensors.