Username Rules
Complete guide to username reservation rules by category. Learn why usernames are restricted and how to check them programmatically.
Username Rules by Category
Username reservation rules are organized by category. Each category explains why certain usernames are restricted and provides examples. Use the username.dev API to check usernames across all categories programmatically.
No need to maintain manual lists—the API stays current with platform policies automatically.
Rule Categories
System & Infrastructure
Technical usernames like admin, root, and api that platforms block to prevent conflicts with core functionality and administrative access.
Brand Names & Trademarks
Trademarked company names and brand identifiers that platforms protect to prevent impersonation and trademark infringement.
Celebrities & Public Figures
Names of famous individuals, influencers, politicians, and public personalities that require identity verification.
Geographic Locations
City names, country names, states, and notable locations that platforms often reserve for official regional accounts.
Government & Official Entities
Government agencies, law enforcement, regulatory bodies, and official institutional identifiers.
Security & Authentication
Security-related terms like login, password, and verify that could be exploited for phishing and credential theft.
Support & Customer Service
Help desk, customer service, and support-related terms that users associate with official assistance channels.
Premium & Short Usernames
High-value short handles, single characters, and desirable terms that platforms reserve for monetization or strategic use.
Unicode & Homoglyph Attacks
Usernames using lookalike characters from different alphabets to impersonate legitimate accounts.
Financial & Banking Terms
Banking, payment, cryptocurrency, and financial service terminology that attracts fraud.
Medical & Healthcare
Healthcare provider terms, medical professional titles, and health-related terminology.
How Username Rules Work
Username rules are applied during registration to prevent conflicts, protect intellectual property, and maintain platform security. Instead of hardcoding rule lists that become outdated:
- Use the username.dev API to check usernames programmatically
- Receive category metadata explaining why usernames are restricted
- Stay current with platform policy changes automatically
- Cover 15+ categories without maintaining separate lists