A trigger is an event within an app that starts a Zap. Once you’ve turned your Zap on, Zapier will check for that trigger event. Zaps can be triggered in two ways: through a regular polling event, or instantly through webhooks.
Why are there different trigger types?
Each app on Zapier has an API that allows other apps, like Zapier, to view and edit its data. Each trigger on Zapier connects to that app’s API to get new information about trigger events.
A trigger event is the information that the trigger is meant to receive, such as a new lead, or a new subscriber on a list.
Most APIs require apps to ask for new information periodically. This is called polling for new information. In Zapier, triggers ask the API if there’s any new information. If there is, the Zap runs. If not, it waits and asks again after a set period, and so on.
Some APIs automatically send new information as those trigger events occur, using webhooks. These are called "instant" triggers. In Zapier, instant triggers wait for new information. When it receives something, the Zap runs.
The type of trigger is defined by each app’s API. Some apps support polling triggers, others support instant triggers, and some support both.
The majority of triggers are polling triggers. They check (or poll) the app for information at regular intervals. The Zap will check if there's new information by comparing the item's unique ID to those it's already received.
The interval it uses to check for data depends on your Zapier plan. The shorter the interval, the faster new information will come through the Zap.
Instant triggers work by using webhooks. Webhooks are automated notifications sent between apps. Whenever there is new information, the app will notify Zapier as soon as it this information is added to the app.
Zaps with instant triggers are labeled "Instant" on your dashboard and in the Zap editor.
Can I change a trigger from polling to instant or the other way around?
It's not possible to change a trigger's type. The trigger type is defined by the app’s API. Most APIs provide ways to poll for new information. To use instant triggers an app must offer webhooks, which send new information to a Zap.
Polling trigger potential issues
The Zap misses information
Polling triggers retrieve a set number of items each time they poll for new information. If the app has more new items than the trigger expects, it may miss some information. The number of items picked up varies depending on the app and the specific trigger used.
The initial poll — the first time a Zap checks for new data when you turn it on — may bring in more information than a regular poll.
If your Zap misses information, you may be able to use Transfer to send these records to the action app.
Old records trigger the Zap
In rare cases a polling trigger cannot recognize that a record is not new and trigger the Zap with previously seen information. This can happen when a large number of items is deleted from the trigger app, causing older items to be surfaced and picked up by the Zap.
In some apps deleting items may change the position of older items (the row where that information is in, for example). This causes the Zap not to recognize that item, as it may use a combination of content and position to recognize duplicates.
If you need to make significant changes to information that's linked to a Zap, it's recommended to turn the Zap off until all changes are completed, and then turn it back on.
Learn more about how to set up a Zap trigger.