You can use the * wildcard in an ACL rule to authorize either any devices and users or any devices and users with specific identifiers to access the topic. The function of this wildcard depends on the topic filter that you use it with.

  • For an identity topic filter, use * to authorize any device or user with an identifier that matches a topic level represented by %c or %u in the topic filter to access this topic.

    For example:

    Topic filterPublishersSubscribers
    company/model/%cEmpty*

    Here the topic filter may represent the following topic company/model/ABC123. The ACL rule authorizes any device with the ABC123 client identifier to subscribe to this topic.

  • For a regular topic filter, use * to authorize any device or user to access the topic.

    For example:

    Topic filterPublishersSubscribers
    company/model/year*Empty

    Here the topic filter represents the following topic company/model/year. The ACL rule authorizes any device or user to publish to this topic.

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You shouldn't use this wildcard with regular topic filters. You should only use this wildcard together with identity topic filters to authorize devices or users with specific identifiers.