Regex for Alphanumeric Username
Regex Pattern
^[a-zA-Z0-9_]{3,16}$Username with letters, digits, underscores (3-16 chars)
Quick Answer
The regex pattern for alphanumeric username is `^[a-zA-Z0-9_]{3,16}$`. Username with letters, digits, underscores (3-16 chars). This works in JavaScript, Python, Ruby, PHP, Java, and most regex engines that support PCRE syntax.
Test Examples
| Input | Result |
|---|---|
| john_doe | ✓ Matches |
| user123 | ✓ Matches |
| alice_99 | ✓ Matches |
| ab | ✗ No match |
| user@name | ✗ No match |
| toolongusernameover16chars | ✗ No match |
Code Examples
javascript
const regex = /^[a-zA-Z0-9_]{3,16}$/;
const isValid = regex.test(value);python
import re
pattern = r'^[a-zA-Z0-9_]{3,16}$'
if re.match(pattern, value):
print("valid")ruby
pattern = /^[a-zA-Z0-9_]{3,16}$/
if value =~ pattern
puts "valid"
endphp
if (preg_match('/^[a-zA-Z0-9_]{3,16}$/', $value)) {
echo "valid";
}java
String pattern = "^[a-zA-Z0-9_]{3,16}$";
boolean isValid = value.matches(pattern);