Checkly generates synthetic test traffic — it runs scheduled API checks and browser flows to verify your endpoint works correctly. Webhook Guardian monitors real traffic — it reads the actual delivery logs that Stripe, Shopify, and GitHub maintain for every webhook they attempt to send. A Checkly API check passing means your endpoint accepts POST requests. Webhook Guardian monitors whether Stripe's actual signed webhook deliveries are succeeding, which synthetic traffic cannot verify.

Checkly vs Webhook Guardian: Synthetic Testing vs Real Delivery Log Monitoring

May 20, 2026 · 7 min read

Checkly and Webhook Guardian both involve monitoring your webhook endpoint — but they operate on fundamentally different data. Checkly generates traffic to test your endpoint. Webhook Guardian reads the real traffic logs that Stripe, Shopify, and GitHub maintain.

The distinction matters because a Checkly API check can pass at the exact same time that Stripe's actual webhook deliveries are failing.

How Does Checkly Work?

Checkly is a synthetic monitoring platform. It runs two types of checks on a schedule: browser checks (using Playwright to simulate user interactions in a headless browser) and API checks (sending HTTP requests to your endpoints and asserting on the response). You write the check logic, configure the schedule and locations, and Checkly runs your checks continuously.

For webhook endpoints specifically, a Checkly API check can POST a test payload to your endpoint, verify that it returns 200, and assert on response headers or body content. This is synthetic traffic — it is not traffic from Stripe, Shopify, or GitHub.

Checkly is excellent for catching regressions: if a deploy breaks your endpoint's ability to accept valid POST requests, a Checkly check will fail and alert you. It is continuous integration applied to your running production endpoints.

How Does Webhook Guardian Work?

Webhook Guardian is a passive delivery log monitor. It generates no traffic of its own. Instead, it connects to Stripe, Shopify, and GitHub via read-only OAuth and polls the delivery logs those platforms maintain for every real webhook event they send.

When Stripe fires an invoice.payment_failed event, Stripe records the outcome in its delivery log — including the HTTP response code, retry count, timestamp, and final status. Webhook Guardian polls this log every 5 minutes. When it detects a failed delivery, it sends a Slack or email alert with the event type, error, retry count, and a one-click replay link.

No synthetic traffic. No test payloads. Only the real events Stripe, Shopify, and GitHub actually sent.

Why Does a Passing Checkly Check Not Mean Stripe Webhooks Are Succeeding?

Checkly verifies that your endpoint accepts POST requests. Stripe's webhooks are not generic POST requests — they include a Stripe-Signature header that your handler must verify using your webhook signing secret. If your signature verification logic has a bug, or if your signing secret rotated without your handler being updated, Stripe's real deliveries will fail — but Checkly's unsigned test payloads will continue to pass.

Similarly, Shopify webhooks include an X-Shopify-Hmac-SHA256 header. GitHub webhooks include an X-Hub-Signature-256. Checkly's synthetic checks cannot replicate these platform-specific signed requests. Webhook Guardian reads the outcome of the real signed requests directly from each platform's delivery log.

How Do Checkly and Webhook Guardian Compare Feature by Feature?

When Should You Use Checkly?

Checkly is the right tool when you want to:

• Run scheduled synthetic checks against your API endpoints to catch regressions before users do
• Simulate browser flows — login, checkout, key user journeys — on a schedule
• Write assertion logic that validates specific response shapes, headers, and latency
• Run monitoring checks from code, stored in version control alongside your application
• Verify that your webhook endpoint structure is correct as part of a CI/CD pipeline

When Should You Use Webhook Guardian?

Webhook Guardian is the right tool when you want to:

• Know when Stripe, Shopify, or GitHub webhook deliveries fail — as recorded by those platforms
• Detect failures caused by signature verification bugs, which synthetic checks cannot reproduce
• Monitor actual real event delivery outcomes, not synthetic test outcomes
• Get the full event payload and a one-click replay link when a real delivery fails
• Set up webhook delivery monitoring in 2 minutes without writing check scripts

Can You Use Both Checkly and Webhook Guardian?

Yes — and this is the recommended approach for teams who want complete webhook coverage. Checkly proactively verifies that your endpoint is correctly handling well-formed requests — catching endpoint regressions before Stripe or Shopify even try to deliver. Webhook Guardian monitors the actual delivery outcomes from Stripe, Shopify, and GitHub as they happen — catching failures in real signed traffic that Checkly's synthetic checks cannot replicate.

Together, they cover both "is my endpoint structurally correct?" and "are the actual platform webhook deliveries succeeding?"

FAQ: Checkly vs Webhook Guardian

Monitor real Stripe, Shopify, and GitHub webhook delivery outcomes — not synthetic test traffic. Start a free 14-day trial and connect via read-only OAuth in 2 minutes — no check scripts to write, no synthetic payloads to configure.

Also comparing: Webhook Guardian vs Better Uptime and Webhook Guardian vs Datadog. See how delivery log monitoring protects SaaS billing workflows and CI/CD pipelines triggered by GitHub webhooks.