Checkfor

Checkfor is a data-verification API that validates email addresses and phone numbers through a single endpoint. It addresses the need for accurate contact data in signup, onboarding, and transaction flows by returning a normalized response that includes a confidence score.

The service performs email verification that covers syntax checks, MX record lookups, detection of disposable and role-based addresses, and optional SMTP mailbox and catch-all probing. For phone numbers it handles E.164 parsing, determines line type and carrier, and conducts live reachability checks via HLR lookups. Every call returns a consistent structure containing a validity flag, a numeric score, the cost in credits, and the remaining balance. Responses arrive in under 300 milliseconds on average and are supported by resilient infrastructure.

A unified credit system applies to both email and phone lookups, with one balance debited atomically per request. When credits are exhausted the API returns a 402 status code. Developers can swap underlying providers without changing their own code. The product is delivered as a REST API that accepts POST requests to a single verify endpoint, with authentication via bearer tokens. It includes a dashboard for monitoring usage and a free tier that grants 100 credits on signup.

Checkfor is intended for developers and businesses that require reliable contact verification. The service operates on a pay-per-lookup pricing model with a unified credit balance.