Inspect Slack Webhooks

Why inspect Slack webhooks?

Slack apps use webhooks to send events (app mentions, messages, slash commands) to your backend. Testing locally requires exposing your development server or using tunnels that expire. WebhookStash provides a persistent endpoint to capture, inspect, and replay Slack events with full signature validation.

Setup

1. Go to WebhookStash.com, sign in with GitHub, and create a project to get your webhook URL.
2. In your Slack app dashboard: Event Subscriptions or Interactivity & Shortcuts.
3. Set Request URL to your WebhookStash endpoint and enable required events (e.g., app_mention, message.channels).
4. Save changes and verify the challenge request.

Trigger and inspect

Invoke a slash command, mention your app, or generate an event in your Slack workspace. Inspect signature headers (X-Slack-Signature), payload JSON, and timestamps in WebhookStash.

Local testing with CLI streaming

Stream webhooks to your localhost using our CLI. View full payloads in the dashboard. This prevents accidental exposure via terminals or screenshots. You can still exercise your local handler:

curl -X POST http://localhost:3000/slack/webhook \
  -H "Content-Type: application/json" \
  -H "X-Slack-Signature: v0=a2114d57b48eac39b9ad189dd8316235a7b4a8d21a10bd27519666489c69b503" \
  -d '{
    "type": "event_callback",
    "team_id": "T01234ABC",
    "event": {
      "type": "app_mention",
      "text": "hello",
      "user": "U01234ABC"
    },
    "token": "xoxb-example-token"
  }'

Replay webhooks from the dashboard to any endpoint, or stream them to localhost using the CLI. so sensitive data never leaves secure server-side boundaries.

Safe replays

• Backend-origin replays to staging/public endpoints
• CLI streaming for localhost testing without exposing tokens
• Authenticated API replays for full payloads when you control the data

Common Slack events to test

• app_mention — When your app is mentioned
• message.channels — Messages in public channels
• slash_commands — Slash command invocations
• reaction_added — Emoji reactions

FAQs

Start inspecting Slack webhooks

No setup. No servers. No hassle.