Next Gen Zap is creating duplicate data

A Next Gen Zap can repeat an action, such as sending the same email twice, when its trigger fires several times close together. Learn why this happens and how to prevent it.

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Symptom

Your Next Gen Zap performs the same action more than once for one record. For example, a contact receives two copies of the same email after you edit their record several times.

To confirm, open your workflow in the Workflow Manager and click the Runs tab at the top of the page. Select each run that repeated the action and check its Input section. If the inputs come from the same record, each run started from a separate trigger event for that record.

Causes

Next Gen Zaps cannot limit a workflow to one run at a time. Zapier skips exact repeats of the same trigger event, but each change to a record starts its own run. Duplicates can happen for the following reasons:

• Quick edits to the same record. An updated record counts as a new trigger event, so each edit starts a run.
• A wait inside the run. The longer a run waits before it acts, such as for 1 hour, the more time later runs have to start for the same record.
• Several workflows that act on the same record. If two Next Gen Zaps trigger on the same record, each one starts its own run.
• An imported Classic Zap that is still on. If you imported a Classic Zap and left the original on, both Zaps run on the same trigger events.

A check for whether the action already happened, such as a search of your sent emails, does not guarantee that only one run acts. Two runs can both check before either one acts.

How to fix it

If you imported a Classic Zap, first turn off the original Classic Zap on your Zaps page.

Then try these options in order. You can ask the AI assistant in the Workflow Manager or your MCP client through Zapier MCP to make each change.

Process records one at a time

1. Ask your AI tool to split your workflow into two Next Gen Zaps.
2. In the first Next Gen Zap, keep your trigger. Have it add each new or updated record to a pending list, such as a Pending tab in a spreadsheet with a blank Status column.
3. In the second Next Gen Zap, run on a schedule, such as every 5 minutes. Have it process the pending records one at a time and mark each one as done before it moves to the next.
4. Ask your AI tool how the second Next Gen Zap handles a run that fails partway or takes longer than the schedule interval.
5. Test both Next Gen Zaps with a test record before you publish them.

Note

A record can wait up to one schedule interval before the second Next Gen Zap processes it. This design reduces overlap, but a scheduled run can still overlap the next one if it takes longer than the schedule interval.

Mark each record after the action

1. Add a field to the record that tracks the action, such as a Result email sent column in your spreadsheet.
2. Ask your AI tool to change the workflow so each run rereads the record right before it acts.
   • If the field has a value, the run stops.
   • If the field is empty, the run writes Sending into the field, performs the action, then changes the value to Sent.
3. Ask your AI tool to make sure that writing to this field does not start the workflow again.
4. Test the workflow with a test record before you publish it.

If a run fails partway, the Sending value tells you which record to check before you retry the action.

This option prevents most repeats, but it is not a guarantee. Two runs that start at almost the same moment can both find the field empty and both act.

Note

Classic Zaps use the Delay After Queue action from Delay by Zapier to process runs one at a time. Next Gen Zaps do not support this action.

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