パスワード生成ツール
強力で安全なランダムパスワードを生成
使い方
値を入力
入力フィールドに数値やパラメータを入力します。
即座に結果を取得
入力するとすぐに結果が更新されます — 送信ボタンは不要です。
コピーまたは保存
結果をクリップボードにコピーするか、ワークフローで活用します。
このツールを使う理由
完全無料
隠れたコストもプレミアムプランもありません — すべての機能が無料です。
インストール不要
すべてブラウザで実行されます。ソフトウェアのダウンロードやインストールは不要です。
プライベート＆安全
データはデバイスの外に出ることはありません。サーバーにアップロードされることはありません。
モバイル対応
完全レスポンシブ対応 — スマートフォン、タブレット、デスクトップで利用できます。
Generating Strong Passwords: Entropy and Best Practices
Key Takeaways
- Password strength is measured in bits of entropy — a strong password should have at least 60–80 bits of entropy.
- Randomly generated passwords with mixed character types are exponentially harder to crack than human-chosen passwords.
- Passwords are generated entirely in your browser using cryptographically secure randomness — they are never stored or transmitted.
Weak passwords remain the number one cause of account compromises. Human-chosen passwords tend to follow predictable patterns that attackers exploit with dictionary attacks and rule-based cracking. A cryptographically random password generator creates truly unpredictable passwords that resist all known attack methods, from brute force to sophisticated AI-powered cracking.
81% of data breaches involve weak or stolen passwords according to the Verizon Data Breach Report.
Breach Statistics
Key Concepts
Password Entropy
Entropy measures password randomness in bits. A password using 26 lowercase letters has log2(26) = 4.7 bits per character. Adding uppercase, digits, and symbols increases entropy to ~6.5 bits per character.
Cryptographic Randomness
This tool uses the browser's crypto.getRandomValues() API, which draws from the operating system's cryptographic random number generator — far superior to Math.random() for security.
Character Set Impact
A 12-character password using only lowercase letters (26 chars) has 56 bits of entropy. Adding uppercase, digits, and symbols (95 chars) jumps to 79 bits — making it 8 million times harder to crack.
Passphrase Alternative
Random word passphrases (like 'correct horse battery staple') offer high entropy with better memorability. Four random words from a 7,776-word list provide approximately 51 bits of entropy.
Pro Tips
Use a minimum of 16 characters for critical accounts — longer passwords exponentially increase the time needed for brute-force attacks.
Use a password manager to store generated passwords — you should never need to memorize random passwords.
Generate unique passwords for every account — password reuse means one breach compromises all your accounts.
Enable two-factor authentication (2FA) alongside strong passwords for defense in depth.
All passwords are generated entirely in your browser using the Web Crypto API's cryptographically secure random number generator. No passwords are stored, logged, or transmitted to any server.