Join a list into a string: join

The join filter concatenates a list of values into a single string, placing a separator between each element. You can also join a specific attribute of a list of objects. This is useful whenever you need to turn a list of items into a readable string. For example, you might want to list the names of 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] that are currently on, build a comma-separated summary for a notification, or join a list of room names for display on a dashboard.

Usage

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

{{ ["living room", "kitchen", "bedroom"] | join(", ") }}

living room, kitchen, bedroom

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.

join(
    value: list,
    separator: str = "",
    attribute: str | None = None,
) -> str

Function parameters

The following parameters can be provided to this function.

Joining without a separator

By default, elements are concatenated directly with no separator between them.

{{ ["a", "b", "c"] | join }}

abc

Good to know

• The default separator is an empty string, so without an argument the items are concatenated directly.
• Each item is converted to a string automatically, so you can join numbers, booleans, and other types.
• Every item must be concrete. Iterables produced by select or selectattr need no conversion, but generators should be materialized first.

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.

List active lights in a notification

Build a human-readable list of lights that are currently on.

{% set lights = ["Living room", "Kitchen", "Porch"] %}
Lights on: {{ lights | join(", ") }}

Lights on: Living room, Kitchen, Porch

Build a path from parts

Join path segments together with a separator.

{{ ["home", "user", "config"] | join("/") }}

home/user/config

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:

• Flatten nested lists: flatten - Flattens nested lists into a single flat list.

• Convert to set: set - Converts an iterable to a set, removing duplicate values.