Topic Names & Filters

Topic Names¶

A topic name is an UTF-8 string containing one or more levels separated by a forward slash character (/). A topic name must not contain any wildcard characters (+ and #)! Topic names are usabe both in publish and subscribe operations.

Example topic names:

Topic Filters¶

Wildcard characters can be used in topic filters to match one or more levels within a topic. MQTT has two types of wildcard characters a Single-level wildcard (+) and a Multi-level wildcard (#).

Single-level wildcard¶

A single-level wildcard can be used to match one level and multiple single-level wildcards can be used in one topic filter.

Multi-level wildcard¶

A multi-level wildcard (#) can be used to match any level in a topic name. # matches its parent level and any number of child levels. When # is used it must be the last character of the topic filter.

Mixed topic filters¶

Single and multi level wildcards can be used in one topic filter:

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