[[trigger]]
== Triggers

Every watch must have a `trigger` that defines when the watch execution process
should start. When you create a watch, its trigger is registered with the
appropriate _Trigger Engine_. The trigger engine is responsible for evaluating
the trigger and triggering the watch when needed.

{watcher} is designed to support different types of triggers, but only time-based
<<trigger-schedule, `schedule`>> triggers are currently available.

:edit_url: https://github.com/elastic/elasticsearch/edit/{branch}/x-pack/docs/en/watcher/trigger/schedule.asciidoc
include::trigger/schedule.asciidoc[]