Introduction

The UserCheck API is organized around REST. It has predictable resource-oriented URLs, returns JSON-encoded responses, and uses standard HTTP response codes and verbs.

If you have not made a request yet, start with the Quickstart.

Base URL

All API requests should be made to:

https://api.usercheck.com

Endpoints

Endpoint	Purpose
GET /domain/{domain}	Signals for a domain
GET /email/{email}	Signals for an email address and its domain
GET /status	Your plan, current usage, and remaining credits
/blocklist	Read and manage your account's custom blocklist

Gates, the rules engine that returns allow or block decisions instead of raw signals, has its own Decision endpoint and a Management API for creating gates and editing rules.

Authentication

Every request must carry an API key in the Authorization header:

curl -X GET "https://api.usercheck.com/email/[email protected]" \
  -H "Authorization: Bearer YOUR_API_KEY"

See Authentication for other ways to pass the key and for examples in other languages.

Errors

Errors return the matching HTTP status code and a JSON body describing what went wrong. From the lookup endpoints:

{
  "status": 400,
  "error": "The domain is invalid."
}

The status codes each endpoint can return are listed on its own page. Requests that exceed your plan's throughput return 429; see Rate Limits.