RelayFox

Slack webhook testing

Test Slack webhooks on localhost—without exposing a port.

Slack sends webhooks for slash commands, interactive components, and event subscriptions. Test your Slack app's event handling locally with RelayFox — no ngrok required. RelayFox keeps receiving if your laptop sleeps, so the original delivery is waiting when you reconnect.

No signup. Disposable URL lasts 24 hours.

Listening live
relayfox.dev/h/...
POSTnow

message

X-Slack-Signature: preserved

Forward when ready

npx relayfox forward <id> --to http://localhost:3000

Inspect the original headers and raw body.
Receive events while localhost is offline.
Forward through one free CLI command.
  1. 1
    Create a free RelayFox URL above (no signup needed).
  2. 2
    Paste it as your webhook endpoint: Slack API Dashboard → Your App → Event Subscriptions / Interactivity → Request URL.
  3. 3
    Trigger an event (e.g. message) and watch it arrive live in RelayFox.
  4. 4
    Run the CLI to forward captured events to your local server:
    npx relayfox forward <endpoint-id> --to http://localhost:3000
  5. 5
    Inspect headers, body and replay any event as many times as you need.

RelayFox preserves the X-Slack-Signature header when forwarding, along with the captured body. Verify against the original raw body. If Slack includes the public destination URL in its signature, configure your verifier with the RelayFox capture URL rather than the localhost forwarding URL.

Ready for the next Slack event?

Create a disposable inbox and paste the URL into Slack.