2026.6.3
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Write to system log

The Write to system log action adds your own entry to the system log. This is handy for debugging automations: you can record that a certain step ran, or log a message at a chosen severity so it stands out in your logs.

Using this action from the user interface

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

To write to the system log from an automation or a script:

  1. Go to Settings > Automations & scenes.
  2. Open an existing automation or script, or select Create automation > Create new automation.
  3. If you’re setting up a new automation, add a trigger in the When section. Scripts don’t need a trigger. They run when something else calls them.
  4. In the Then do section, select Add action.
  5. From the search box, search for and select System Log: Write to system log.
  6. Enter the Message, and optionally a Level and a Logger.
  7. Select Save.

This action does not support targets. In the UI, you are not prompted to choose an area, device, entity, or label.

Options in the UI

Message (Required)

The message to write to the log.
Level (Optional)

The severity to log the message at. One of debug, info, warning, error, or critical. Defaults to error.
Logger (Optional)

The logger name to write the message under. Defaults to homeassistant.components.system_log.external.

Using this action 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.

In YAML, refer to this action as system_log.write. A basic example looks like this:

ActionActions are used in several places in Home Assistant. As part of a script or automation, actions define what is going to happen once a trigger is activated. In scripts, an action is called *sequence*. [Learn more] 
action: system_log.write
data:
  message: "Something went wrong"
  level: error

This writes the message Something went wrong to the log at the error level.

Options in YAML

message string Required

The message to write to the log.

level string

The severity to log the message at. One of debug, info, warning, error, or critical.

logger string

The logger name to write the message under.

Default:

homeassistant.components.system_log.external

Try it yourself

Ready to test this? Open Developer tools > Actions, search for this action, fill in the fields, and select Perform action. You see what happens 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] without writing a line of YAML.

Still stuck?

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

Tip

AI assistants like ChatGPT or Claude can also explain actions or suggest the right one when you describe what you want in plain language.

Related actions

These actions work well alongside this one:

  • Clear system log: Clears all stored entries from the Home Assistant system log.