2026.10.4
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Set a default value: default

The default filter returns a fallback value when the variable it is applied to is undefined. If the optional boolean parameter is set to true, it also replaces values that are falsy (empty strings, 0, false, none, and empty collections). This is one of the most commonly used template filters.

In Home Assistant templates, you frequently work with variables that may or may not exist depending on the context. For instance, triggerA trigger is the part of an automation that makes the automation start when something specific happens, for example, when the sun sets, a door opens, or a button is pressed. [Learn more] variables are only available when the automationAutomations in Home Assistant allow you to automatically respond to things that happen in and around your home. [Learn more] actually runs, and custom variables from {% set %} blocks may be conditionally defined. The default filter lets you write robust templates that always produce a usable value, even when some inputs are missing or empty.

Usage

Here’s how to use this template function. Copy any example and adjust it to your setup.

As a filter 
{{ my_variable | default("fallback") }}
Result (stringA piece of text, like a name, message, or entity ID. In templates, wrap strings in quotes, like "living_room" or "lights are on".) 
fallback

Function signature

The signature is a technical summary of this template function. It shows the name of the function, the values (called parameters) it accepts, and what type of data each parameter expects (for example, a piece of text or a number).

Function parameters that have a = with a value after them are optional. If you leave them out, the default value shown is used automatically.

Function parameters without a = are usually required. A few optional parameters have no default value, so the signature shows them without a = as well. To check whether a parameter is required, look at the parameter list below the signature. Each parameter is marked as Required or Optional.

The most common optional parameter without a default value is default. The default parameter sets the value a function returns when the function can’t produce a result, for example, when float gets text that isn’t a number. If you leave out default, there is no fallback value, so most functions raise an error and the template fails. The parameter list of each function says what happens. If you set default, the function returns your value instead.

How to read a signature

Here is the signature of the round filter as an example:

round(
    value: Any,
    precision: int = 0,
    method: str = "common",
    default: Any,
) -> float | int | Any
  • round is the name of the function.
  • Between the parentheses are the parameters. Each parameter has a name, followed by a colon and the type of value the parameter expects. The type only tells you what kind of value to pass. For default: Any, you pass a value of any type, such as 0 or "unknown", not the word Any.
  • = 0 and = "common" are default values. You can leave out precision and method, and round uses these default values.
  • default has no =, but the parameter list marks default as optional. If you leave out default and round gets a value that isn’t a number, round raises an error.
  • -> shows the type of value the function returns.
  • Inside a signature, | means “or”. This function returns a decimal number, a whole number, or the value you passed as default.

round is a filter, so the first parameter, value, is the value before the |. For example, {{ 3.14159 | round(2) }} returns 3.14.

The types you’ll see most often:

  • str: text, such as "hello"
  • int: a whole number, such as 5
  • float: a decimal number, such as 3.14
  • bool: true or false
  • list: a list of values, such as [1, 2, 3]. list[str] is a list of texts.
  • dict: a set of keys and values, such as {"name": "Kitchen"}
  • datetime and timedelta: a date and time, and a duration. For details, refer to Dates and times.
  • None: no value
  • Any: any type of value

Some signatures use special forms:

  • *args means you can pass any number of values, separated by commas. For example, average(1, 2, 3).
  • value | name(...) means the function is a filter. The value before the | is passed to the filter as its first parameter. Some filter signatures, like the round example, show this value as the first parameter between the parentheses instead.
value | default(
    default_value: Any = "",
    boolean: bool = false,
) -> Any

Function parameters

The following parameters can be provided to this filter.

default_value any (Optional, default: “”)

The value to return if the input is undefined (or falsy, when boolean is true). Defaults to an empty string.

boolean boolean (Optional, default: false)

If true, the filter also replaces falsy values (false, 0, none, empty strings, and empty collections) with the default. If false (the default), only undefined variables are replaced.

Handling undefined variables

When a variable has not been defined, the default filter returns the fallback value instead of raising an error.

TemplateA template is an automation definition that can include variables for the action or data from the trigger values. This allows automations to generate dynamic actions. [Learn more]: Undefined variable gets fallback 
{{ undefined_var | default("no value") }}
Result (stringA piece of text, like a name, message, or entity ID. In templates, wrap strings in quotes, like "living_room" or "lights are on".) 
no value

Replacing falsy values with boolean mode

When boolean is set to true, the filter also replaces empty strings, 0, false, none, and empty lists.

TemplateA template is an automation definition that can include variables for the action or data from the trigger values. This allows automations to generate dynamic actions. [Learn more]: Empty string replaced in boolean mode 
{{ "" | default("empty!", true) }}
Result (stringA piece of text, like a name, message, or entity ID. In templates, wrap strings in quotes, like "living_room" or "lights are on".) 
empty!
TemplateA template is an automation definition that can include variables for the action or data from the trigger values. This allows automations to generate dynamic actions. [Learn more]: Zero replaced in boolean mode 
{{ 0 | default(42, true) }}
Result (integerA whole number without decimal places, like 1, 42, or -5. Used for counts, indices, and whole values.) 
42

Good to know

  • Without boolean=true, the default only kicks in for undefined variables. None, empty strings, and 0 pass through unchanged.
  • The default value for default_value is an empty string, not None.
  • default can’t protect a chain of attributes on an undefined value. For example, if trigger is undefined, {{ trigger.to_state.state | default("unknown") }} raises an error before default runs.
  • This does not catch unavailable or unknown entity states, since those are defined strings. Combine with has_value or float for those cases.

Try it yourself

Ready to test this? Open Settings > Tools > Template, paste the example into the Template editor, and watch the result update on the right. Edit the values to see how the function adapts to your own 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 function comes up in automations and templates. Copy any example and adapt it to your setup.

Safe access to trigger data

TriggerA trigger is the part of an automation that makes the automation start when something specific happens, for example, when the sun sets, a door opens, or a button is pressed. [Learn more] variables are only available when the automationAutomations in Home Assistant allow you to automatically respond to things that happen in and around your home. [Learn more] runs. When you test a template outside an automation, trigger is undefined. Reading trigger.to_state then raises an error before default runs. Some triggers also have no to_state, for example, when you select Run actions. And when an entity is removed, to_state is none. This example covers all three cases. default(none) turns a missing to_state into none, so you don’t get a warning in the log.

TemplateA template is an automation definition that can include variables for the action or data from the trigger values. This allows automations to generate dynamic actions. [Learn more]: Safely access trigger state 
{% set to_state = trigger.to_state | default(none)
     if trigger is defined else none %}
{{ to_state.state if to_state else "unknown" }}
Result (stringA piece of text, like a name, message, or entity ID. In templates, wrap strings in quotes, like "living_room" or "lights are on".) 
unknown

Provide a default sensor value

When an entity might not have a specific attribute, provide a sensible default. state_attr returns none for a missing attribute. Pass true as the second argument so default also replaces none.

TemplateA template is an automation definition that can include variables for the action or data from the trigger values. This allows automations to generate dynamic actions. [Learn more] 
{{
  state_attr("climate.living_room", "preset_mode")
  | default("none", true)
}}
Result (stringA piece of text, like a name, message, or entity ID. In templates, wrap strings in quotes, like "living_room" or "lights are on".) 
comfort

Fallbacks for numeric states

states always returns text, even for a missing entity. It returns unknown in that case, so default has nothing to replace. To make sure calculations don’t fail, use the default argument of float or int instead.

TemplateA template is an automation definition that can include variables for the action or data from the trigger values. This allows automations to generate dynamic actions. [Learn more] 
{{ states("sensor.temperature") | float(0) + 5 }}
Result (floatA number that can have decimal places, like 21.5 or 3.14. Used for temperatures, percentages, and other measurements that need precision.) 
26.5

Use in an automation action

Set a notification message with a fallback greeting when the name is not set. An empty text helper has an empty string as its state. Pass true as the second argument so default also replaces the empty string.

ActionAn action makes Home Assistant do something, for example, turn on a light, send a notification, or activate a scene. Automations and scripts run a list of actions. [Learn more] 
action:
  - action: notify.mobile
    data:
      message: >
        Hello {{ states("input_text.user_name") | default("friend", true) }}!

Still stuck?

The Home Assistant community is quick to help: join Discord for real-time chat, post on the community forum with your template and expected result, or share on our subreddit /r/homeassistant.

Tip

AI assistants like ChatGPT or Claude can also explain or fix templates when you describe what you want in plain language.

Related template functions

These functions work well alongside this one: