Quick Summary — TL;DR
A webhook relay is an intermediary service that sits between a webhook sender and the final destination. It receives webhook requests, then forwards them to one or more target URLs. The sender delivers to the relay's stable URL, and the relay handles getting the data where it actually needs to go — whether that's your local machine, multiple endpoints, or a transformed version of the original payload.
External services can't reach localhost. When you're developing a Stripe integration and need to receive payment webhooks on your local machine, a relay bridges the gap. You point Stripe at the relay's public URL, and the relay forwards requests to your local development server through a tunnel.
Tools like ngrok, Cloudflare Tunnels, and dedicated webhook relay services all solve this problem. They give you a public URL that tunnels requests to a port on your machine. For testing without any tunnel, you can use a webhook tester to inspect payloads first, then replay them against your local endpoint.
Some webhook providers only let you register a single URL per event type. If you need the same event delivered to multiple services — your main application, an analytics pipeline, a logging service — a relay can receive the webhook once and fan it out to all destinations. Each destination gets its own copy of the request.
If your application goes down for maintenance or has an outage, incoming webhooks fail. Most providers retry, but they have limits — after enough failures, they may disable your webhook endpoint entirely. A relay can absorb webhooks during downtime, store them, and deliver them once your application is back up. This gives you a buffer layer that decouples webhook receipt from processing.
When the sender's payload format doesn't match what your application expects, a relay can transform the data in transit. Convert XML to JSON, flatten nested structures, rename fields, filter out irrelevant data — all without changing either the sender or receiver. This is especially useful when integrating with legacy systems or bridging between services with incompatible payload formats.
The terms overlap, but there's a general distinction:
In practice, most relay services add gateway-like features over time — filtering, transformation, delivery logs. The line between relay and gateway is blurry. If you just need to forward webhooks to localhost or fan out to a couple of endpoints, a simple relay is enough. If you're managing webhook traffic for a production platform with dozens of integrations, you probably want gateway-level features.
The most common use of webhook relays is local development. The typical workflow:
https://abc123.ngrok.io forwards to localhost:8000).This lets you develop and test webhook handlers against real event data without deploying to a staging environment. For a detailed walkthrough, see our guide on how to test webhooks locally.
A webhook relay is an intermediary service that receives webhooks from a sender and forwards them to one or more destination URLs. It acts as a middleman that can buffer, duplicate, transform, or route webhook traffic between the original sender and the final receivers.
Direct delivery is fine when you have a single, always-available endpoint. A relay helps when your endpoint isn't always reachable (localhost, behind a firewall, during deployments), when you need to fan out to multiple destinations, when you want to buffer during downtime, or when you need to transform the payload format before it reaches your application.
Use a tunneling tool like ngrok or Cloudflare Tunnels. These tools create a public URL that forwards HTTP traffic to a port on your local machine. Register the public URL as your webhook endpoint with the external service, and requests will be tunneled to your local development server. See our guide on testing webhooks locally for step-by-step instructions.
A webhook relay sits between the webhook sender and your inbound webhook endpoint, forwarding requests reliably. When your application is the sender, the relay becomes part of your outbound webhook delivery pipeline. Use a webhook tester to inspect what the relay is forwarding, and verify signatures carefully if the relay modifies payloads in transit.
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