Domain name restrictions vary by extension and country association.
General Rules
- Character composition: Domains can be formed using only letters and numbers from the ASCII set (a–z, A–Z, 0–9). Hyphens are also allowed but must be surrounded by characters
- Uniqueness: The domain must not already be registered
- Length limits: Standard extensions (.com, .net, .org, .info) cannot exceed 67 characters; most other extensions are capped at 22 characters excluding the extension
- Minimum characters: .info and .biz require at least 3 characters before the extension
- Case insensitivity: Domain names are not case-sensitive
- Two-letter prohibition: Domains with only two letters are not permitted
Common Extensions
- .com — commercial/personal
- .net — infrastructure companies
- .org — non-profits
- .biz — business-only
- .mobi — mobile-optimised sites
Country-Specific Extensions
- .ca — Canada
- .co.uk — UK commercial
- .eu — European Union presence
- .jp — Japan