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.

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.