Tunnels, networking, testing, and inspection
Hands-on guides for local tunnels, webhook testing, inbound email, and inspecting HTTP traffic before it hits your handler — from the people building Mercur.
Inspect WebSocket traffic on a localhost tunnel
Inspect handshake and frames on a Mercur WebSocket tunnel, share the session, and debug CORS that is actually a 503 from the relay.
What is a webhook?
A webhook is an HTTP callback that pushes event data to your URL. Learn how webhooks work, how they differ from APIs, and how to test them locally.
Temporary mailboxes for inbound email testing
Get a temporary @mercur-mail.com inbox in Mercur. Inspect inbound messages, download attachments, and optionally forward parsed JSON to an HTTP endpoint.
Create a Telegram bot with webhooks
Create a BotFather bot, handle updates on a local Node.js weather server, and point Telegram’s webhook at a Mercur HTTPS URL so deliveries reach localhost.
Connect Cursor to Mercur remote MCP
Create a workspace API key, connect an MCP client to Mercur remote MCP, and inspect tunnel request history from the IDE.
Test GitHub webhooks locally
Configure a GitHub repository webhook against a public URL, inspect ping and push deliveries, tunnel events to localhost, and replay stored requests from the console.
How to test webhooks
Test and debug webhooks with a public HTTPS URL: inspect method, headers, and body, forward to localhost with the macOS app or npm CLI, then replay a stored delivery from the console.
Test Stripe webhooks locally
Point a Stripe webhook endpoint at a public URL, inspect the event payload, forward deliveries to your local app, and replay stored events from the console.