Build, validate, and format webhook payloads for testing integrations. Create sample payloads for GitHub, Stripe, Slack, and custom webhooks — all in your browser.
Webhook Tester is a free tool for building, validating, and formatting webhook payloads. It includes templates for popular services like GitHub, Stripe, and Slack, so you can quickly generate realistic test payloads. The tool validates JSON syntax, calculates payload size, and formats the output for readability — all in your browser with no server required.
Use Webhook Tester when developing webhook receivers, testing integration endpoints, or creating sample payloads for documentation. It is especially useful during the development phase when you need realistic test data without triggering actual events in third-party services like GitHub or Stripe.
Developers use this tool to construct webhook payloads for local testing with tools like ngrok, validate JSON payload structure before sending to production endpoints, generate sample payloads for API documentation and README files, format and inspect webhook payloads captured from logs, and verify payload sizes stay within receiver limits.
Essential terms and definitions related to Webhook Tester.
An HTTP callback that sends real-time data from one application to another when a specific event occurs. Unlike APIs where you poll for data, webhooks push data to your endpoint automatically. Common uses include payment notifications (Stripe), repository events (GitHub), and messaging integrations (Slack).
The body of data sent in a webhook HTTP request, typically formatted as JSON. The payload contains the event details — for example, a GitHub push webhook payload includes the commit messages, author information, repository details, and the list of changed files.
A cryptographic signature (Hash-based Message Authentication Code) used to verify that a webhook payload was sent by the expected service and was not tampered with in transit. The sender computes HMAC-SHA256 of the payload using a shared secret, and the receiver recomputes it to verify authenticity.
No. This is a client-side payload builder and validator. It helps you construct, format, and validate webhook payloads before sending them to your application for testing. For receiving live webhooks, you would need a server-side endpoint or a service like webhook.site.
The tool includes templates for common services: GitHub (push, pull request, issue events), Stripe (payment, subscription events), Slack (message, interactive events), and a generic JSON webhook template. You can also create fully custom payloads.
The tool validates JSON syntax and structure. It checks that your payload is valid JSON, displays it formatted for readability, and highlights any syntax errors. For schema-specific validation, you would use the JSON Schema Generator tool in combination.
Copy the generated payload and use it with cURL, Postman, or any HTTP client to send a POST request to your webhook endpoint. The cURL to Code tool can help you generate the exact request code in your preferred language.
Common errors developers encounter and how to resolve them.
Invalid JSON syntax in payload Common JSON errors include trailing commas after the last property, single quotes instead of double quotes, unquoted property names, and missing commas between properties. The tool highlights the exact location of syntax errors to help you fix them.
Webhook signature verification fails Many services (GitHub, Stripe) sign webhook payloads with HMAC-SHA256. The signature depends on the exact byte content of the payload — even whitespace changes will produce a different signature. When testing, ensure you use the raw (non-prettified) payload for signature computation.
Payload too large or deeply nested Most webhook receivers have payload size limits (typically 5-25 KB). If your test payload is very large or deeply nested, it may be rejected. Keep test payloads realistic and within the size limits specified by the receiving service.