Integration
SimpleCold for Webhooks
Stop polling. Add an HTTPS endpoint, pick the events, and SimpleCold POSTs signed JSON when a slow check settles, a bulk job finishes or your credits run low.
What it does
What the Webhooks integration does
What works today, and nothing more.
result.ready
A single or batch check that answered processing gets its final result pushed, with the same fields as the API. One event per request, never one per address.
bulk.finished and bulk.progress
bulk.finished when a job completes, fails or is canceled, with counts per category, credits used and download paths. Optional bulk.progress at most every 30 seconds.
Signed and retried
Every request carries SimpleCold-Signature (HMAC-SHA256 over the timestamp and raw body). Failures retry 8 times over 24 hours with the same event id.
Setup
Set it up in 3 steps
A few lines of code on your side. The docs have copy-paste verification samples.
- 01
Add an endpoint
In Settings → Webhooks, enter a public https URL and choose events: result.ready, bulk.finished, bulk.progress or credits.low. Or create it with your API key.
- 02
Verify the signature
Copy the whsec_ secret, shown once. Check SimpleCold-Signature against the raw body and reject timestamps older than 5 minutes. The docs have Node, Python and PHP code.
- 03
Send a test event
Click Send test event to get a ping, then watch status, attempt, response code and latency in the delivery log. Resend any event for 30 days.
On every request
Headers we send
The body is JSON with id, type, created, orgId and data. Answer with any 2xx within 10 seconds.
| Header | What it holds |
|---|---|
| SimpleCold-Signature | t=<unix seconds>,v1=<hex HMAC-SHA256 of t.rawBody>; two v1 values for 24 hours after a secret rotation |
| SimpleCold-Event-Id | The evt_ id. The same on every retry and resend, so you can dedupe |
| SimpleCold-Event-Type | result.ready, bulk.finished, bulk.progress, credits.low or ping |
| SimpleCold-Webhook-Version | The payload version, 2026-10-26 |
| SimpleCold-Delivery-Id, SimpleCold-Delivery-Attempt | This delivery and its attempt number |
| User-Agent | SimpleCold-Webhooks/1.0 |
Use another tool?
The REST API works now: single, batch and bulk endpoints with an API key. Or upload a CSV from any tool.
FAQ
Webhooks questions
Short answers.
Still have a question? Talk to us.
Check your list before you send it
Start with 200 free credits. Pay per credit after that.