WhoSignup

WhoSignup is a developer-friendly tool that sends instant notifications when high-value users sign up for your SaaS.

Instead of getting pinged for every free Gmail signup, you send your signup events to WhoSignup via a simple REST API. We enrich the data (company, size, domain authority, etc.) and only notify you when a signup matches rules you define.

Perfect for: founders and devs who want to do fast, personal outreach to valuable leads without building this logic in-house.

- Simple REST API: POST your signup data from any stack - Instant email alerts: get notified within seconds - Smart rules: filter by company size, domain authority and more - Automatic enrichment: extra context for better outreach

Example:

POST https://api.whosignup.com/signups
Authorization: Bearer YOUR_API_KEY
Content-Type: application/json
{
  "email": "user@example.com",
  "first_name": "Jane",
  "last_name": "Doe",
  "company": "Acme Inc"
}

Set it up once, define your criteria, and never miss an important signup again.