Why webhooks cause duplicates
Payment webhooks are messages your payment provider sends to notify your store of events, like a successful payment, so your system can create the order. They are essential, but they come with a catch: providers retry webhooks if they are unsure you received them, which can deliver the same event more than once. If your store naively creates an order per webhook, retries cause duplicate orders. Understanding retries, verification, ordering, and idempotency is how you handle webhooks correctly and prevent duplicates reliably.
Delivery retries are normal
The root cause of duplicates is that delivery retries are a normal, intentional part of how webhooks work: if the provider does not get a clear success response (due to a timeout, error, or network hiccup), it resends the event to ensure you are not missing it. This is good for reliability, you will not lose events, but it means your system must expect to receive the same event multiple times. Designing for repeated delivery, rather than assuming each webhook arrives exactly once, is the foundation of handling them safely.
Verify signatures
Before acting on any webhook, verify its signature: payment providers sign their webhooks so you can confirm the message genuinely came from them and was not forged or tampered with. Acting on an unverified webhook is dangerous, since an attacker could send fake events (like a fake 'payment succeeded'). Signature verification ensures you only process authentic events from your provider. This security step is essential and must come before any order processing, so you never act on a fraudulent or altered webhook.
Event ordering and idempotency keys
Two concepts prevent duplicates and confusion. Event ordering: webhooks may arrive out of order, so your system should handle events sensibly regardless of sequence rather than assuming perfect order. Idempotency keys are the key defense: each event carries a unique identifier, and by recording which event IDs you have already processed, you can safely ignore repeats, processing each logical event only once no matter how many times it is delivered. Using idempotency keys to deduplicate is what reliably prevents retries from creating duplicate orders.
Reconciliation and a test plan
As a safety net, use reconciliation: periodically compare your records against the provider's to catch any discrepancies, missed or duplicated events, and correct them. And test thoroughly with a plan covering the tricky cases: duplicate events (same event sent twice, should create one order), delayed events (arriving late or out of order), and failed events (ensuring proper handling and retries). Testing these scenarios, plus reconciliation as a backstop, ensures your webhook handling is genuinely robust against the real-world behavior of retries and out-of-order delivery.
The bottom line
Payment webhooks prevent duplicate orders when you treat delivery retries as normal, verify signatures before acting, handle event ordering gracefully, and use idempotency keys to process each event only once, with reconciliation as a safety net. Test duplicate, delayed, and failed events. Because providers legitimately resend webhooks, building for repeated, out-of-order delivery is what keeps your store from creating duplicate orders and acting on fraudulent events.
Related on Skillo
See also: How to improve checkout reliability on an e-commerce website, What is a webhook? Explained.
Sources
Published date reflects the original event date (2026-10-23). This article is original Skillo editorial written from the sources above; facts were verified in September 2026.
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