Automation Answers

Why Is My Webhook Firing Twice?

A webhook can arrive twice because the sender retries after a timeout, multiple subscriptions target the same endpoint, or both test and production.

By Automation Ace Editorial TeamReviewed for technical accuracy by Troy TessalonePublished Updated

Short answer

Why Is My Webhook Firing Twice?

A webhook can arrive twice because the sender retries after a timeout, multiple subscriptions target the same endpoint, or both test and production workflows are active. Compare event IDs, delivery timestamps, and subscription IDs; acknowledge quickly, then deduplicate processing with the provider event ID.

Common causes

  • The receiver responds too slowly, so the sender retries delivery.
  • Two webhook subscriptions listen to the same event.
  • A proxy or automation relay forwards the same payload more than once.
  • The workflow has no idempotency check for event IDs.

Diagnostic steps

  1. Capture headers, payload event ID, timestamps, and sender delivery logs for both requests.
  2. List all active subscriptions and workflows pointing at the endpoint.
  3. Return a successful response quickly and move slow work behind a queue when possible.
  4. Store each event ID before side effects and skip IDs already processed.

Example

A payment provider times out waiting for a response and retries the same event. Both requests share an event ID, so an idempotency check prevents a second fulfillment.

Caveats

Do not deduplicate only by timestamp or customer email; two legitimate events may share those values. Verify webhook signatures before trusting event IDs.