How to Safely Receive Webhooks: Verification, Deduplication, and Ordering

Receiving webhooks introduces security and reliability challenges that are often invisible until a system reaches production. Because webhook endpoints are public URLs, anyone can send forged payloads unless each request is verified using a shared secret and a timing-safe signature comparison. A common implementation mistake is verifying a re-serialized JSON body instead of the original raw bytes, which can cause signature mismatches due to changes in key order or whitespace. Developers must also account for retries and out-of-order delivery, since processing the same event twice or in the wrong sequence can corrupt real application state. These principles apply broadly to webhooks from providers like Stripe, GitHub, and Shopify, not just email delivery services.