[Yandex Cloud documentation](../../../index.md) > [Yandex IoT Core](../../index.md) > [Concepts](../index.md) > [Topic](index.md) > Subtopic

# Subtopic

{% note warning %}

Yandex IoT Core is no longer available to new users. 

Current users can create resources until November 1, 2026. Afterwards, the service will go read-only and cease to operate on December 1, 2026. For more information on the timing and procedure, see [Service shutdown](../../sunset.md).

{% endnote %}

A _subtopic_ is a custom topic created within existing device and registry topics. You do not need to create a subtopic, just start sending messages to it.

Everything that comes after a device or registry topic and separated by `/` is considered a subtopic:  

```text
<device_or_registry_topic>/<subtopic_name>
```

Examples of subtopics: 
* `$devices/<device_ID>/events/bedroom/temperature`: Subtopic to receive bedroom temperature data.
* `$devices/<device_ID>/state/bedroom/temperature`: Subtopic to receive bedroom temperature data, which stores the most recent message sent to this subtopic.
* `$registries/<registry_ID>/commands/bedroom`: Subtopic to send commands to all devices in the bedroom.
* `$registries/<registry_ID>/config/bedroom`: Subtopic to send commands to all devices in the bedroom, which stores the last message sent to this subtopic.

Subtopics are based on the same [operating principles](usage.md) and [limits](../limits.md) as topics.