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

Safe

Test String

No matches

john_doe
user-123
alice
web_dev_42

^^— ^ — start of string (or line in multiline mode)

[…]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'

(?!…)Negative lookahead (?!…)— Negative lookahead — asserts the following text does NOT match this pattern (zero-width)

.*.— . — matches any character except newline (unless 's' flag is set) — repeated zero or more times (greedy) · * — zero or more times (greedy)

[…]{2}Character class […]— Matches any single character listed in this set — repeated exactly 2 times · {2} — exactly 2 times

[…]{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

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'

__— '_' — literal character

\-\-— \- — escaped character

[…]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'

$$— $ — end of string (or line in multiline mode)

Pattern: 57 charsInput: 34 chars

100% client-side · private

✓ Valid Examples

Validate Username natively in your backend or frontend without copying regex strings.

import { validate } from '@regexto/validators';

validate('username', '...');

from regexto_validators import validate

validate("username", "...")

import "github.com/regex-to/validators-go"

valid, err := validators.Validate("username", "...")

use RegexTo\Validators\Validator;

Validator::validate('username', '...');

use regexto_validators::validate;

let is_valid = validate("username", "...").unwrap();