Password Generator Tool - Secure Random Password and Passphrase Generator with Strength Checker

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This tool generates cryptographically secure random passwords and passphrases using the Web Crypto API (crypto.getRandomValues()). You can also check the strength of any password with entropy-based analysis and estimated crack time.

All processing is performed entirely in your browser using client-side JavaScript. No data is transmitted to any server. Your passwords never leave your device.

  • This tool is provided "AS IS" without any warranties of any kind.
  • The author accepts no responsibility for any security incidents arising from the use of generated passwords.
  • Password strength estimates are approximate and based on brute-force attack models.
  • Always use unique passwords for each account and consider using a password manager.
  • By using this tool, you accept full responsibility for any outcomes.

This tool uses client-side JavaScript for all processing. No data is transmitted to servers, no passwords are stored or logged, all processing happens locally in your browser. Once loaded, this tool continues to work even without an internet connection. For more details, please refer to our Web Tools Disclaimer.

Password Options

16

Enter a password to check its strength

Features

  • Cryptographically Secure: Uses the Web Crypto API (crypto.getRandomValues()) for true random number generation, not Math.random().
  • Character-Based Passwords: Customizable length (8-128 characters) with selectable character sets — uppercase, lowercase, digits, and symbols.
  • Passphrase Mode: Generate memorable passphrases from a curated word list with customizable separators, capitalization, and optional numbers.
  • Strength Checker: Analyze any password's entropy, character class composition, and estimated brute-force crack time.
  • Batch Generation: Generate 1, 5, 10, or 20 passwords at once with individual copy buttons.
  • Ambiguous Character Exclusion: Option to exclude easily confused characters (0/O, 1/l/I) for better readability.
  • Pattern Detection: Identifies sequential characters, repeated characters, keyboard patterns, and common passwords.
  • 100% Client-Side: All processing happens in your browser. No data is transmitted to any server.
  • Works Offline: Once loaded, the tool works without an internet connection.

How to Use

  1. Generate a Password: Select "Password" mode, adjust the length and character set options, then click "Generate".
  2. Generate a Passphrase: Switch to "Passphrase" mode, set the number of words, separator style, and options, then click "Generate".
  3. Copy to Clipboard: Click the "Copy" button next to any generated password to copy it.
  4. Check Password Strength: Switch to the "Check Strength" tab, enter or paste a password, and click "Analyze" (or just type — analysis updates in real-time).
  5. Batch Generate: Use the "Generate count" dropdown to create multiple passwords at once.

Important Notes

  • This tool uses the Web Crypto API for cryptographically secure random number generation with rejection sampling to eliminate modulo bias.
  • Strength estimates assume a brute-force attack at 10 billion guesses per second. Actual security depends on many factors including how the password is stored and transmitted.
  • The passphrase word list contains approximately 800 common English words. Passphrase entropy is calculated based on the word list size and number of words.
  • Generated passwords are never stored, logged, or transmitted. They exist only in your browser's memory until the page is closed or cleared.
  • Always use unique passwords for each account. Consider using a password manager to store your passwords securely.
  • A modern browser with Web Crypto API support is required (all major browsers since 2015).

References:
Tech Blog with curated related content
Web Tools Collection

Written by Hidekazu Konishi