Username

Matches a valid username: 3–20 characters, letters, digits, hyphens, and underscores. No leading/trailing hyphens or underscores.

✓ User registration✓ Social media handles✓ API key naming

Test String

4 matches

john_doe
user-123
alice
web_dev_42

[…]Character class […]— Matches any single character listed in this set

a-za-z— a-z — range from 'a' to 'z'

A-ZA-Z— A-Z — range from 'A' to 'Z'

0-90-9— 0-9 — range from '0' to '9'

(?:…)?Non-capturing group— Non-capturing group — groups without capturing (no index assigned) — repeated zero or one time (optional) · ? — zero or one time (optional)

[…]{1,18}Character class […]— Matches any single character listed in this set — repeated between 1 and 18 times · {1,18} — between 1 and 18 times

[…]Character class […]— Matches any single character listed in this set

Pattern: 47 charsInput: 34 chars

100% client-side · private

✓ Valid Examples

john_doe
user-123
alice
web_dev_42

✗ Invalid Examples

-john
john-
_user
a
this_username_is_way_too_long_for_any_system