Checking domain availability is more nuanced than a simple yes/no query. Premium domains, reserved names, and different TLD policies all affect availability. Understanding these factors helps build better domain search tools.
How Availability Checking Works
Domain availability APIs query registrar databases using the WHOIS protocol or EPP (Extensible Provisioning Protocol). If a domain is registered, the query returns registration details. If available, it returns no record. However, some registrars flag availability checks and may "front-run" domains you search for (registering them speculatively).
Reserved and Restricted Domains
Some domains are permanently reserved (example.com is reserved for documentation). Others require eligibility verification (.edu requires accreditation, .gov requires government authorization). Country-code TLDs often have residency requirements. Availability APIs may show these as "unavailable" or "restricted."
Alternative TLD Suggestions
When a .com is taken, suggest alternatives: .io (popular with tech startups), .co (commerce/company), .net (network/tech), .ai (artificial intelligence), .app (applications), and country-codes (.us, .uk, .ca). Modern TLDs like .dev, .tech, and .online are also viable. The best alternative depends on the use case and brand identity.