Password Strength Checker

Analyze password strength with scoring, requirements check, and actionable feedback.

Installation

npm install password-strength-checker

Quick Start

import { analyze, getScore, getFeedback } from 'password-strength-checker';

const result = analyze('MyP@ssw0rd');
console.log(result.score);    // 75
console.log(result.strength); // 'strong'
console.log(result.feedback); // ['Consider using 12+ characters...']

API

Quick Score

getScore('password')    // 15 (very weak)
getScore('Str0ng!Pass') // 80 (very strong)

getStrengthLevel(85)    // 'very-strong'
getStrengthLevel(65)    // 'strong'
getStrengthLevel(45)    // 'medium'
getStrengthLevel(25)    // 'weak'
getStrengthLevel(10)    // 'very-weak'

Character Checks

hasLowercase('abc')     // true
hasUppercase('ABC')     // true
hasNumbers('123')       // true
hasSpecialChars('!@#')  // true
isCommonPassword('password')  // true
hasSequential('abc123') // true
hasRepeated('aaa')      // true

Entropy Calculation

calculateEntropy('password')  // ~38 bits
calculateEntropy('Str0ng!Pass123') // ~72 bits

Requirements Check

const result = checkRequirements('MyPass1!', {
  minLength: 8,
  requireUppercase: true,
  requireNumbers: true,
  requireSpecialChars: true
});

// { minLength: { passed: true, message: 'At least 8 characters' }, ... }

Feedback

getFeedback('weak')
// ['Use at least 8 characters', 'Add uppercase letters', ...]

getFeedback('Str0ng!Password123')
// ['Great password!']

Full Analysis

const analysis = analyze('Test123!');
// {
//   score: 65,
//   strength: 'strong',
//   entropy: 52,
//   feedback: [...],
//   requirements: { ... },
//   checks: { hasLowercase: true, ... }
// }

License

MIT