Printf-style string formatting: format

The format filter applies printf-style string formatting to a template string, replacing placeholders like %s (string), %d (integer), and %f (float) with the provided values. This is the same formatting style used in many programming languages. This is useful when you want to build a formatted string with multiple dynamic values inserted at specific positions. For example, you might want to format a notification message with a sensor name and its value, or create a display string with a number formatted to a specific number of decimal places.

Usage

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

{{ "Hello %s, you have %d messages" | format("Alice", 5) }}

Hello Alice, you have 5 messages

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 default are required.

format(
    value: str,
    *args: Any,
    **kwargs: Any,
) -> str

Function parameters

The following parameters can be provided to this function.

Formatting numbers

Use %d for integers and %f for floats. You can control decimal places with %.Nf.

{{ "Temperature: %.1f degrees" | format(22.456) }}

Temperature: 22.5 degrees

Good to know

• Uses printf-style specifiers, not Python f-strings or {0} positional placeholders.
• Type must match: %d with a non-integer raises an error. Cast with int or float first.
• A literal percent sign in the output requires %% in the format string.

Try it yourself

Ready to test this? Open Developer 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.

Build a notification message with sensor data

Create a formatted notification message combining multiple sensor values.

{{
  "The %s is %.1f°C with %d%% humidity"
  | format("living room", 22.5, 65)
}}

The living room is 22.5°C with 65% humidity

Format a zero-padded number

Use %03d to pad a number with leading zeros.

{{ "Sensor ID: S-%03d" | format(7) }}

Sensor ID: S-007

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.

Related template functions

These functions work well alongside this one:

• Replace occurrences in a string: replace - Replaces all occurrences of a substring with another string.

• Truncate text to a length: truncate - Truncates a string to a given length, appending an ellipsis if it was shortened.