Webhook Tester

The Webhook Tester is a free, client-side tool designed for developers who work with webhook integrations. Whether you need to inspect a payload from Stripe, verify a GitHub signature, or simulate a POST request to your own endpoint, this tool handles it all within your browser — no data ever leaves your machine.

What Is a Webhook?

A webhook (also called an HTTP callback or web callback) is an automated HTTP POST request that a service sends to your application when a specific event occurs. Instead of your application repeatedly polling an API for updates, the service proactively pushes event data to a URL you configure. Webhooks power real-time integrations across payment processing, version control, messaging, CI/CD pipelines, and more.

Key Features

How to Use This Tool

1. Choose a mode: Select one of four tabs — Payload Inspector, Signature Verifier, Request Simulator, or Sample Webhooks.
2. Enter your data: Paste a webhook payload, enter a signature to verify, configure a request, or pick a sample webhook from popular services.
3. Run the action: Click the action button to parse, verify, send, or load the selected webhook data.
4. Review results: Examine the parsed tree view, verification result, response details, or formatted sample payload.

Webhook Security: Why Signatures Matter

When a webhook is sent over the internet, there's no guarantee that the payload came from the service you expect. An attacker could forge a request to your endpoint with a malicious payload. HMAC signatures solve this problem: the sender computes a hash of the payload using a shared secret, and includes it in a header. Your server recomputes the hash and verifies it matches — if it does, the payload is authentic and untampered.

Common signature headers include X-Hub-Signature-256 (GitHub), Stripe-Signature (Stripe), and X-Slack-Signature (Slack). Our Signature Verifier tab lets you test this process directly in the browser.

Common Webhook Providers

GitHub

GitHub sends webhooks for repository events like pushes, pull requests, issues, releases, and more. Signatures use HMAC-SHA256 with the X-Hub-Signature-256 header.

Stripe

Stripe sends payment event webhooks (charges, subscriptions, invoices). They use a timestamp-based signature scheme with the Stripe-Signature header containing t= and v1= components.

Slack

Slack sends interaction payloads and event subscriptions. Signatures use HMAC-SHA256 with the X-Slack-Signature header and a versioned signing scheme (v0: prefix).

Discord

Discord interaction webhooks include Ed25519 signatures. Event payloads contain interaction data for slash commands, buttons, and modals.

Twilio

Twilio sends status callbacks for SMS, voice calls, and other communications events. Payloads are typically form-encoded with fields like MessageSid, From, and Body.

Frequently Asked Questions

What is a webhook?

A webhook is an HTTP callback that sends real-time data from one application to another when a specific event occurs. Instead of polling an API repeatedly, webhooks push data to your endpoint automatically, making them efficient for event-driven architectures.

How do I verify a webhook signature?

Webhook signatures are verified by computing an HMAC hash of the payload using a shared secret key and comparing it to the signature sent in the request header. Use the Signature Verifier tab to paste your payload, secret, and received signature to check if they match.

Is my webhook data safe with this tool?

Yes. All processing happens entirely in your browser using client-side JavaScript. No webhook payloads, secrets, or signatures are ever sent to our servers. Your data stays on your machine.

What webhook providers does this tool support?

The Sample Webhooks tab includes pre-built payloads for GitHub, Stripe, Slack, Discord, and Twilio. The Payload Inspector and Signature Verifier work with any JSON webhook payload from any provider.

Can I send test webhook requests from this tool?

Yes. The Request Simulator tab lets you send HTTP POST requests with custom headers and a JSON body to any publicly accessible URL. Note that the target server must allow cross-origin requests (CORS) for the browser to receive the response.

Additional Resources

• GitHub Webhooks Documentation
• Stripe Webhooks Guide
• Slack Incoming Webhooks