Light brightness crossed threshold

The Light brightness crossed threshold trigger fires when the brightness of a light entityAn entity represents a sensor, actor, or function in Home Assistant. Entities are used to monitor physical properties or to control other entities. An entity is usually part of a device or a service. [Learn more] crosses into a zone you define. Use it to react to a light rising above a level, dropping below a level, entering a range, or leaving a range, like starting an automation only once brightness rises above 50%. Brightness is measured as a percentage of full brightness, from 0 to 100.

Unlike Light brightness changed, which fires on every change that matches the threshold, this trigger only fires at the moment the brightness crosses into the zone. It does not fire again until the brightness leaves the zone and crosses into it again.

When you target more than one light, the trigger’s Trigger when option controls when it fires.

Using this trigger from the user interface

If you prefer building automations visually, Home Assistant walks you through this trigger step by step. You pick what to watch, tweak a few options, and save. No YAML knowledge required.

To use Light brightness crossed threshold in an automation:

1. Go to Settings > Automations & scenes.
2. Open an existing automation, or select Create automation > Create new automation.
3. In the When section, select Add trigger.
4. Select what you want to monitor. Under By target (see Targets), pick the area your light is in (like your living room or bedroom). You can also select a device, a specific entity, or a label.
5. From the triggers shown for that target, select Light brightness crossed threshold.
6. Under Threshold type, configure the zone the reading must enter for the trigger to fire:
   • Select Above or Below and enter a value to fire when the reading crosses that level.
   • Select In range and enter a lower and upper bound to fire when the reading enters the range from outside.
   • Select Outside range and enter a lower and upper bound to fire when the reading leaves the range (crosses past either bound).
   • For each option, you can enter a fixed percentage (0–100%), pick a sensor entity or a number helper entity as the threshold.
     • If you don’t have a number helper, you can create one by selecting Create a new number helper.
7. Under Trigger when (see Behavior), pick Each, First, or All to control how the trigger behaves when multiple entities are targeted.
8. Under For at least, set how long the reading must stay past the threshold before the trigger fires. Leave it at zero to fire immediately.
9. Select Save.

Options in the UI

Using this trigger in YAML

If you work directly in YAML, or you want to know exactly what Home Assistant does under the hood, this section has the technical reference. It lists the field names you use in YAML, their types, and which ones are required.

When this trigger starts an automation, it passes data about what happened to the automation. You can use this trigger data in the templates of your conditions and actions. To see which data is available, refer to Trigger data in templates.

In YAML, refer to this trigger as light.brightness_crossed_threshold. A basic example looks like this:

trigger: light.brightness_crossed_threshold
target:
  entity_id: light.living_room
options:
  threshold:
    type: above
    value:
      number: 50

This fires when the living room light’s brightness rises above 50%.

Options in YAML

threshold:
  type: above
  value:
    number: 50

Targets of the trigger

This trigger requires a target. The target is the object that Home Assistant will watch. You can select a single entityAn entity represents a sensor, actor, or function in Home Assistant. Entities are used to monitor physical properties or to control other entities. An entity is usually part of a device or a service. [Learn more], a device, an area, a floor, or a label as a target, and Home Assistant will watch every matching light entity behind that target.

• Entity: one specific light entity, such as light.living_room.
• Device: every light entity that belongs to a device.
• Area: every light entity in a room or area.
• Floor: every light entity on a floor.
• Label: every light entity that shares a label.

You can also select different target types in one trigger. For example, you can add a specific entity and an area as targets in the same trigger to monitor both of them at once.

To learn which entities Home Assistant includes for a device, area, floor, or label, and how it handles several entities, refer to Automation targets.

Trigger variables

When the trigger fires, the trigger variable identifies the entity that caused it to fire. This is useful when a target contains multiple entities, such as a device, area, floor, or label.

The following trigger-specific variables are available:

For example, use {{ trigger.to_state.name }} in an action to include the name of the entity that caused the trigger in a notification.

The trigger variable describes the entity that caused the trigger to fire; it does not contain all entities resolved from the configured target.

Behavior with multiple targets

When you target more than one entity (or select an area, floor, or label that contains several), the Trigger when option controls how the trigger responds:

• Each (default): the trigger fires every time any one of the targeted entities transitions. For example, if you monitor three motion sensors in the living room and someone walks past sensor 1, the automation fires. When they walk past sensor 2 a moment later, it fires again. Every individual event counts.
• First: the trigger fires only on the first transition in the targeted group, then waits until none of the targeted entities is in that state anymore before it fires again. For example, if you monitor the same three motion sensors, the automation fires when the first one picks up movement (someone entered the room). The other two firing afterward are ignored, so you get one notification per “someone walked in” event instead of three.
• All: the trigger fires only after the last targeted entity in the group has fired, meaning all of them are now in the expected state. For example, if you monitor the lights in the living room, bedroom, and hallway, the automation fires only once all three have turned off. This is useful for scenarios like “start the robot vacuum only after every light on the floor is off,” so you know the room is truly empty.

Good to know

• The threshold type sets the direction. With Above, the trigger fires when the brightness rises above the threshold. With Below, it fires when the brightness drops below it.
• A light that is off has no brightness value. Turning a light off does not fire the trigger, not even with Below. Turning a light on fires the trigger if the new brightness is inside the zone, for example, turning a light on at 70% fires an Above 50% trigger.
• If you use an entity as the threshold, it must report its value in percent (%). An entity with a different unit, or no unit, is ignored and the trigger does not fire.
• Pair this trigger with Light brightness in follow-up conditions to double-check the final state.

Try it yourself

Ready to test this? Go to Settings > Automations & scenes, create a new automation, and add this trigger. Save the automation, then change the state of the targeted entity to watch the trigger fire on your actual entitiesAn entity represents a sensor, actor, or function in Home Assistant. Entities are used to monitor physical properties or to control other entities. An entity is usually part of a device or a service. [Learn more].

More examples

Real scenarios where this trigger fires in automations and scripts. Copy any example and adapt it to your setup. In the visual editor, select the UI options listed in the example when they are available, or paste the YAML code.

Automation: start mood lighting when the ceiling light dims below 40%

When you dim the ceiling light below 40% in the evening, turn on the accent lighting so the room feels layered instead of dim.

• Trigger: Light brightness crossed threshold
  • Target: Living room ceiling light
  • Threshold type: Below 40%
  • Trigger when: Each
• Condition: Sun is below horizon
• Condition: Light brightness
  • Target: Living room ceiling light
  • Threshold type: Below 40%
• Action: Turn on light (accent lights)

alias: "Mood lighting on dim"
triggers:
  - trigger: light.brightness_crossed_threshold
    target:
      entity_id: light.living_room_ceiling
    options:
      threshold:
        type: below
        value:
          number: 40
conditions:
  - condition: sun
    after: sunset
  - condition: light.is_brightness
    target:
      entity_id: light.living_room_ceiling
    options:
      threshold:
        type: below
        value:
          number: 40
      behavior: any
actions:
  - action: light.turn_on
    target:
      entity_id: light.living_room_accent
    data:
      brightness_pct: 60
      color_name: warm_white

Still stuck?

The Home Assistant community is quick to help: join Discord for real-time chat, post on the community forum with the trigger you’re using and what you expected to happen, or share on our subreddit /r/homeassistant.

Related triggers

Explore related triggers:

• Light brightness changed: Triggers when the brightness of one or more lights changes.

• Light turned on: Triggers when one or more lights turn on.