Documentation / HTTP Inspector

HTTP Inspector

Capture, inspect, replay, and manipulate HTTP traffic flowing through your tunnel

Quick Start

The inspector is built into every HTTP tunnel. Open the inspector URL shown when you start a tunnel to see requests in real time. 

$ stunl -port 3000

  ● STUNL

  ╭── ◎ ── HTTP
  │   HTTPS       https://abc123.stunl.io
  │   Inspector   https://portal.stunl.com/inspect/abc123
  │   Local       localhost:3000

Request Capture

Every request through your tunnel is captured with full details, streamed to the inspector UI via WebSocket in real time.

Captured Data

• Method
• Path
• Headers
• Request body
• Status code
• Duration
• Bytes uploaded
• Bytes downloaded

Filtering

Narrow down captured requests using built-in filters.

  • • Method -- filter by GET, POST, PUT, DELETE, etc.
  • • Status range -- filter by 2xx, 4xx, 5xx, or specific codes
  • • Path search -- text search across request paths

Replay

Re-send any captured request to your local server with one click.

Instant Replay

Click replay on any captured request to send the exact same request again. Rate limited to 10 replays per minute with SSRF protection.

Edit & Replay

Modify the method, path, headers, or body before replaying. Useful for testing edge cases or fixing a payload without waiting for the external service to send a new request.

Advanced Rules

Configure rules to intercept, mock, or manipulate traffic flowing through your tunnel.

Breakpoint Rules Pro

Pause requests that match a method and path pattern. While paused, you can inspect the request and choose to forward it, modify it, or drop it entirely. 

Match:  POST /api/webhooks/*
Action: pause → inspect → forward / modify / drop
Mock Rules Pro

Return fake responses without the request ever reaching your local server. Configure the status code, headers, and response body. 

Match:   GET /api/health
Return:  200 {"status": "ok"}
Headers: Content-Type: application/json
Chaos Rules Pro

Inject failures to test your application's resilience. Add latency, random errors, or custom error responses.

Parameter Description
latency Additional delay in milliseconds
error rate Probability of error (0 to 1)
error status HTTP status code for injected errors
error body Response body for injected errors

Webhook Verification

The inspector automatically detects and verifies webhook signatures from popular providers. No configuration needed -- just send webhooks through your tunnel and see verification status in the inspector.

Supported Providers

• Stripe
• GitHub
• Slack
• Shopify
• Linear

Snapshots & Export

Snapshots Pro

Share captured requests via a public link. Snapshots include full request and response details and expire after 7 days. Useful for sharing webhook payloads with teammates or filing bug reports.

Export Formats

Export any captured request as a command or code snippet. Copies directly to your clipboard.

curl
curl -X POST https://abc123.stunl.io/api/data \
  -H "Content-Type: application/json" \
  -d '{"key": "value"}'
HTTPie
http POST https://abc123.stunl.io/api/data \
  key=value
fetch (JavaScript)
fetch("https://abc123.stunl.io/api/data", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({ key: "value" })
})

Free vs Pro

Feature Free Pro
Request capture & filtering ✓ ✓
Export (curl, HTTPie, fetch) ✓ ✓
Webhook verification ✓ ✓
Replay & Edit+Replay -- ✓
Breakpoint rules -- ✓
Mock rules -- ✓
Chaos rules -- ✓
Snapshots (7-day public links) -- ✓

Next Steps