Overview

UserCheck is a domain intelligence API. You send it a domain or an email address and it returns signals about that address: whether the domain runs a disposable email service, whether it forwards to another mailbox, whether it can receive mail at all, how old it is, and more.

There are two lookup endpoints. Both are stateless GET requests that return JSON.

GET https://api.usercheck.com/domain/{domain}
GET https://api.usercheck.com/email/{email}

What you do with the signals is up to your application. If you would rather define rules in a dashboard and receive an allow or block decision instead of raw signals, see Gates.

Where to start

If you want to	Go to
Make your first request	Quickstart
Look up a field in the response	Domain endpoint, Email endpoint
Understand what a signal means	Concepts
Get allow or block decisions instead of raw signals	Gates
Be notified when a domain's status changes	Webhooks
Add UserCheck without writing code	Integrations
Know what a request costs	Credits

For AI and coding agents

The full documentation is available in a machine-readable format at llms.txt. Every page also serves raw markdown, either by appending .md to its URL or by sending an Accept: text/markdown request header.