Receive alerts by webhook

1. Have an endpoint ready

Any https URL that accepts a POST and answers with a 2xx status within 8 seconds: your own service, a serverless function, or a catch hook in a no-code tool (n8n Webhook node, Zapier Webhooks by Zapier → Catch Hook, Make Webhooks → Custom webhook).

It must be reachable from the internet: Mortemain refuses private and internal addresses, and does not follow redirects, so give it the final URL.

2. Add the target in Mortemain

In your Mortemain dashboard, add a notification target:

• Type → Webhook
• Name → anything you'll recognise, e.g. Incident bridge
• URL → your endpoint

Save, then wire it to the checks you care about.

3. What Mortemain sends

On every state change of a wired check, one POST with Content-Type: application/json and an Idempotency-Key header:

{
  "check": "Nightly backup",
  "check_id": "6f1c2b9e-0d4a-4e8b-9a51-2c7f3e1d8b40",
  "transition": "down",
  "title": "🔴 Nightly backup · DOWN",
  "body": "Mortemain: \"Nightly backup\" is DOWN (missed its expected check-in) as of 2026-10-19 02:30 GMT+2.",
  "at": "2026-10-19T00:30:00.000Z",
  "at_local": "2026-10-19 02:30 GMT+2",
  "idempotency_key": "4812:1"
}

• transition: what happened, as a stable code that is never translated. Branch on this one. down (missed its check-in, grace over), late (overdue, still inside grace), fail (the job reported a failure), up (recovered), flapping (keeps toggling between healthy and late or down), auth_reject (a check-in was refused; only if you turned that alert on for the check).
• check and check_id: the check's name and its stable id (the one in the check's dashboard URL).
• title and body: ready-to-display text, in the language of the project owner.
• at: when it happened, ISO 8601 in UTC. at_local: the same instant in the project owner's timezone.
• idempotency_key: the same value as the header.

4. Delivery and retries

Any 2xx answer counts as delivered. Anything else, a timeout or a redirect counts as a failure and is retried with a growing delay (30 seconds, then doubling, at most an hour apart), up to 8 attempts. A target that keeps failing shows an undelivered count on your dashboard.

Each attempt carries its own Idempotency-Key: receiving the same key twice means the same attempt arrived twice, so drop the duplicate. Answer quickly and do the real work afterwards, so a slow reply never turns into a retry.

Test it

Hit Test on the target. Your endpoint receives a sample alert for a check named Mortemain test alert, with transition up. If it does not arrive, the target shows the error your endpoint returned.