Regex for Username Validation
Quick Answer: A common username regex: ^[a-zA-Z][a-zA-Z0-9_-]{2,29}$. This requires: starts with a letter, allows letters/digits/underscores/hyphens, and is 3-30 characters long. Adjust the character set and length to match your application requirements.
FAQ
What characters should usernames allow?
Most apps allow letters, digits, underscores, and sometimes hyphens or dots. Start with letters to avoid confusion with numeric IDs. Case-insensitive comparison prevents impersonation.
Should I restrict username length?
Yes. Minimum 3 characters prevents meaningless names. Maximum 30 characters prevents abuse. Twitter uses 4-15, GitHub uses 1-39, Reddit uses 3-20.