How to Test Mailchimp Webhooks
Mailchimp webhooks notify your application when subscribers join, update, unsubscribe, or when campaigns are sent.
Looking for the broader picture? See the 7 best webhook testing tools (2026), or if you're already on Webhook.site, the 60-second migration to HookRay.
Mailchimp Official Webhook Docs1. Mailchimp Webhook Events
Mailchimp can send the following webhook events to your endpoint:
subscribeunsubscribeprofilecleanedupemailcampaign2. Set Up a Test Endpoint with HookRay
Follow these steps to start receiving Mailchimp webhooks for testing:
- Go to HookRay and click "Start Testing — Free" to get your unique webhook URL.
- Copy the URL (e.g.,
https://h.hookray.com/abc123). - In your Mailchimp dashboard, navigate to the webhook settings and paste the HookRay URL as your endpoint.
- Select the events you want to receive (see list above).
- Trigger a test event — HookRay will show the incoming webhook in real-time.
3. Sample Mailchimp Webhook Payload
Here's an example of what a Mailchimp webhook payload looks like:
{
"type": "subscribe",
"fired_at": "2026-03-20T12:00:00+00:00",
"data": {
"id": "8a25ff1d98",
"email": "new-subscriber@example.com",
"email_type": "html",
"list_id": "a6b5c4d3e2",
"merges": {
"FNAME": "Casey",
"LNAME": "Rivera"
}
}
}4. Frequently Asked Questions
How do I test Mailchimp webhooks without deploying?
Use HookRay to get an instant public webhook URL. Paste it into your Mailchimp dashboard's webhook configuration, trigger an event, and watch the payload arrive in real time. No code, no ngrok, no deployment required. The free tier captures 100 requests per month and works on all Mailchimp event types.
Why aren't my Mailchimp webhooks arriving?
The four most common causes: (1) the endpoint URL isn't publicly accessible — Mailchimp can't reach localhost; (2) the wrong events are subscribed in your Mailchimp dashboard; (3) signature verification is rejecting the request before your handler runs; (4) Mailchimp can't reach your server because of a firewall, expired SSL certificate, or wrong DNS. Use HookRay's URL to isolate which of these four is failing — if HookRay receives the webhook, the problem is in your handler. If HookRay doesn't, the problem is in Mailchimp configuration.
Why am I getting 400 or 500 errors from my Mailchimp webhook?
Mailchimp reports the response status your endpoint returned. HookRay accepts any payload and returns 200 OK by default, so if you see 400/500 in your Mailchimp dashboard while pointing at HookRay, the issue is in Mailchimp's configuration (wrong event, malformed signing secret, etc.). If you point at your own endpoint and get 400/500, the issue is in your handler — capture the request with HookRay, replay it locally, and debug from the captured payload.
How do I verify Mailchimp webhook signatures?
Mailchimp signs each webhook request with a shared secret. Capture the raw headers and body using HookRay, then verify the signature in your application using Mailchimp's SDK or a standard HMAC library. Once verification works against HookRay-captured data, you can safely deploy. Mailchimp's docs (linked above) cover the exact signing algorithm.
Can I replay a captured Mailchimp webhook?
Yes — HookRay's replay feature re-sends any captured webhook to a different endpoint with one click. This is the fastest way to fix a buggy handler: capture the payload once, fix your code, and replay until it works. No need to re-trigger the event in Mailchimp.
5. Next Steps
- Use HookRay's webhook replay feature to re-send captured webhooks while building your handler
- Enable smart parsing (Pro plan) to see Mailchimp-specific fields highlighted automatically
- Check the Mailchimp webhook documentation for the complete event reference
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Start Testing Mailchimp Webhooks — FreeFree PDF: Webhook Testing Cheat Sheet 2026
One-page reference for 50+ APIs — canonical events, signing methods, sample payloads. Print it, pin it, share it.
📄 Download the cheat sheet (PDF, 180KB)