Alphanumeric Validation Regular Expression

Alphanumeric validation ensures that input contains only letters (A-Z, a-z) and digits (0-9). This is commonly used for usernames, identifiers, product codes, and other fields where only basic ASCII letters and numbers are permitted. The pattern strictly validates ASCII characters and does not support Unicode letters, accented characters, or special symbols.

Recommended Solution

^[a-zA-Z0-9]+$

Explanation

^ - Start of the string.
[a-zA-Z0-9]+ - Matches one or more characters that are either uppercase letters (A-Z), lowercase letters (a-z), or digits (0-9).
$ - End of the string.

Note: This pattern uses ASCII character ranges and does not support Unicode characters. If you need to support international characters (e.g., ñ, é, 你, Ж), consider using Unicode character classes like \p{L} and \p{N} where supported, or a more permissive pattern.

Implementation

const regex = /^[a-zA-Z0-9]+$/;
const isValidAlphanumeric = (input) => regex.test(input);

import re

def is_valid_alphanumeric(input):
  regex = r"^[a-zA-Z0-9]+$"
  return re.match(regex, input) is not None

use regex::Regex;

fn is_valid_alphanumeric(pattern: &str) -> bool {
  let regex = Regex::new("^[a-zA-Z0-9]+$")
    .expect("Could not parse alphanumeric validation regex");
  regex.is_match(input)
}

package main

import (
  "regexp"
)

func isValidAlphanumeric(input string) bool {
  regex := "^[a-zA-Z0-9]+$"
  re := regexp.MustCompile(regex)
  return re.MatchString(input)
}

import Foundation

func isValidAlphanumeric(_ pattern: String) -> Bool {
  let regex = "^[a-zA-Z0-9]+$"
  return NSPredicate(format: "SELF MATCHES %@", regex).evaluate(with: input)
}

using System;
using System.Text.RegularExpressions;

class Application {
  static bool IsValidAlphanumeric(string input) {
    string regex = "^[a-zA-Z0-9]+$";
    return Regex.IsMatch(input, regex);
  }
}

import java.util.regex.*;

public class Application {
  public static boolean isValidAlphanumeric(String input) {
    String regex = "^[a-zA-Z0-9]+$";
    Pattern pattern = Pattern.compile(regex);
    Matcher matcher = pattern.matcher(input);
    return matcher.matches();
  }
}

<?php
function isValidAlphanumeric($input) {
  $regex = "^[a-zA-Z0-9]+$";
  return preg_match("/" . $regex . "/", $input);
}
?>

Test Cases

Input	Valid
abc123
ABC
123
Test123
a1b2c3
0
Z
(empty string)
abc-123
abc_123
abc 123
abc.123
abc@123
hello world
test!
user@domain
ñoño
café
你好
привет