Cron events with no action

You may see cron events listed with a value of "None" in the Action column. This means the cron event is scheduled to run at the specified time but there is no corresponding functionality that will be triggered when the event actually runs. It's usually safe to delete these events, but read on for further information.

What causes this and how can I fix it?

Deactivated plugins

Events with no actions are most commonly caused by plugins that don't clean up their scheduled events when you deactivate them. If an event is scheduled by a plugin during activation but doesn't unschedule it during deactivation, the event will remain in place but because the plugin is no longer active there is nothing hooked in to perform an action when the event runs. The event simply becomes non-operational.

You can use your favourite search engine to search for the hook name in order to find out which plugin it belongs to, and then decide whether or not to delete it. Deleting such an event is usually safe because most plugins reschedule their events should you decide to reactivate it in the future.

Conditionally registered actions

Occasionally a plugin will register the actions for its cron events only when the cron runner is about to process the cron events that are due (when the DOING_CRON constant is defined). This means that during normal operation -- for example viewing the list of cron events via the Cron Events screen in WP Crontrol -- the action for an event will not be registered and won't be shown despite the fact it will be registered when the event actually runs. This is not particularly common, but it does happen, and unfortunately there's nothing that WP Crontrol can do to alert you to this.

Similarly to the above, you can use your favourite search engine to search for the hook name in order to find out which plugin it belongs to, and then decide whether to delete it or retain it.

Logic errors in plugins

It could also be that a plugin on your site contains a straight forward logic error which means it has registered a cron event but no corresponding action. Quite rare, but it happens. If this appears to be the case then you should report the problem to the author of the affected plugin.