Capture, inspect, and replay webhook requests

When a webhook misbehaves, the hard part is usually reproducing it. The provider fired once, your handler threw, and now you're staring at a stack trace with no way to make the same request happen again. Yellorn closes that loop: capture the real request at a live URL, inspect exactly what arrived, then replay it against your own handler as many times as you need — all in the browser, no CLI and nothing to install.

Publish any payload as a mock endpoint (see What is a mock API webhook) and you get a public HTTPS URL on Cloudflare's edge. Point the provider — Stripe, GitHub, Shopify, or your own service — at that URL, or copy it as a curl command to fire a test by hand. Every hit is recorded in an owner-only log.

Open a request in the log and every detail is there: the HTTP method, the URL query parameters, the full request headers, and the raw body. The body viewer has Raw, Whitespace, and Hex modes, so an invisible-character bug — a stray \r, the wrong line ending, a mangled multipart boundary — is obvious instead of hidden (see Fix multipart/form-data 400 errors). This is the ground truth of what your client actually sent, not what you assume it sent.

Click the Send action in the request's toolbar and a composer opens, already filled in with the captured method, headers, and body. Type a destination URL — a local tunnel, a staging server, or another service entirely — and click Send. Yellorn dispatches the request and shows you the response inline: status code, latency, response size, and the body in the same Raw / Whitespace / Hex viewer.

"Include captured headers" is on by default, so a provider's signature header and the original User-Agent ride along unchanged — the destination sees the request as if the provider sent it. Framing headers (host, content-length) and Yellorn's loop-guard header are stripped automatically so the replayed request is always valid.

The request is dispatched from Cloudflare's edge, which can't reach localhost or a private IP on your network. To replay against a server on your own machine, expose it with a tunnel — ngrok, Cloudflare Tunnel, or similar — and point the destination at the public tunnel URL. The request then arrives at your local handler byte-for-byte as the original did, so you can step through it in a debugger.

The composer is fully editable before you send. Change the method, toggle the captured headers off to test without a signature, or edit the body to reproduce an edge case or fix a malformed field. Each Send is a fresh request, so you can iterate: tweak, send, read the response, tweak again — no waiting for the upstream provider to fire another event.

Need the request somewhere else? The same toolbar copies it as a ready-to-run cURL command or a JSON object, or opens it in the editor, where you can convert, repair, or diff it against another payload.

Yellorn deliberately does not forward every incoming webhook automatically. Auto-forwarding would put an unreliable second hop on your capture endpoint's critical path, invite retry storms, and hand abusers a relay. A manual, explicit replay is the opposite: it happens only when you click Send, against a URL you chose, exactly once. That keeps the capture endpoint fast and predictable while giving you a precise debugging tool — the request you want, resent when you want it.

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