What Makes a Generated Password Truly Strong?

A good secure password generator has one essential property: it produces output with high entropy. Entropy is a measure of unpredictability — how many possible combinations an attacker must try before finding your password. More entropy means harder to crack.

Entropy is measured in bits. Each bit doubles the search space. A 50-bit password has 2⁵⁰ possible combinations — about 1 quadrillion. A 128-bit password has 2¹²⁸ — more combinations than atoms in the observable universe. Modern cracking rigs running bcrypt at 10,000 hashes/second would take trillions of years.

Random Password vs Passphrase — Which Is Better?

Random Character Passwords

A fully random password using uppercase, lowercase, digits, and symbols from a pool of ~95 characters gives approximately 6.5 bits of entropy per character. A 16-character fully random password gives ≈ 104 bits — effectively uncrackable with current technology.

    
Example: 16-char random passwordsCopy
    // Generated with cryptographic randomness
K#9mP$vQ2xLn@8wR    // ~104 bits entropy
7!fBzN%sYkR3@qDm    // ~104 bits entropy
Xp&4Lw9!Jm#2cKv@    // ~104 bits entropy

// All practically uncrackable — but hard to memorize
  

Passphrases (Diceware Method)

A passphrase chains random dictionary words. Each word from a 7,776-word Diceware list adds 12.9 bits. Four words = 51.7 bits. Five words = 64.6 bits. Six words = 77.5 bits — comparable to a 12-char random password but far easier to remember.

Dos and Don’ts of Password Security

Generate Secure Passwords in Code

JavaScript — Cryptographically Secure

    
JavaScript — Cryptographically SecureCopy
    // Cryptographically secure password generator
function generatePassword(length = 16, options = {}) {
  const {
    uppercase  = true,
    lowercase  = true,
    digits     = true,
    symbols    = true
  } = options;

  let chars = '';
  if (uppercase)  chars += 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
  if (lowercase)  chars += 'abcdefghijklmnopqrstuvwxyz';
  if (digits)     chars += '0123456789';
  if (symbols)    chars += '!@#$%^&*()_+-=[]{}|;:,.<>?';

  // Use crypto.getRandomValues — NOT Math.random()
  const array = new Uint32Array(length);
  crypto.getRandomValues(array);

  return Array.from(array, n =>
    chars[n % chars.length]
  ).join('');
}

generatePassword(16);
// → "K#9mP$vQ2xLn@8wR"

generatePassword(24, { symbols: false });
// → "7fBzNsYkR3qDmXpLw9JmcKv4"

// Passphrase generator (requires a word list)
function generatePassphrase(wordList, count = 5) {
  const indices = new Uint32Array(count);
  crypto.getRandomValues(indices);
  return Array.from(indices, n =>
    wordList[n % wordList.length]
  ).join('-');
}
// → "correct-horse-battery-staple-river"
  

Python

    
PythonCopy
    import secrets
import string

# Cryptographically secure password generator
def generate_password(length=16):
    alphabet = (
        string.ascii_letters +
        string.digits +
        '!@#$%^&*()_+-=[]{}|;:,.<>?'
    )
    return ''.join(secrets.choice(alphabet) for _ in range(length))

print(generate_password(20))
# → "K#9mP$vQ2xLn@8wRqTfB"

# Passphrase (Diceware-style)
def generate_passphrase(word_list, count=5):
    return '-'.join(secrets.choice(word_list) for _ in range(count))

# Estimate entropy of any password
import math

def estimate_entropy(password):
    pool = 0
    if any(c.islower() for c in password): pool += 26
    if any(c.isupper() for c in password): pool += 26
    if any(c.isdigit() for c in password): pool += 10
    if any(c in string.punctuation for c in password): pool += 32
    return math.log2(pool) * len(password)
  

Password Managers — Use One With Every Password You Generate

The best practice in password security is pairing a good generator with a password manager. It stores and autofills unique strong passwords for every account — you only need to remember one master password.

Frequently Asked Questions