How is password strength calculated?

Password strength is calculated using entropy (bits of randomness based on character pool size and length), plus bonuses for meeting security criteria like length thresholds, character diversity, and absence of common patterns.

What makes a password strong?

A strong password is at least 12 characters long and includes uppercase letters, lowercase letters, numbers, and special symbols. It should also avoid common words, sequential patterns like '123' or 'abc', and repeated characters.

Is my password sent to a server?

No. All analysis happens entirely in your browser using client-side JavaScript. Your password is never transmitted over the network, ensuring complete privacy.

What is password entropy?

Entropy measures the unpredictability of a password in bits. It is calculated as log2(pool size) multiplied by password length, where pool size is the number of possible characters used. Higher entropy means a harder-to-crack password.

How long should my password be?

Security experts recommend at least 12 characters for most accounts and 16+ for sensitive ones. A 16-character password using all character types has over 100 bits of entropy, making brute-force attacks computationally infeasible.

パスワード強度チェッカー

エントロピー分析、解読時間の推定、詳細な基準確認でパスワードの強度を即座に測定します。

使い方

エントロピー分析、解読時間の推定、詳細な基準確認でパスワードの強度を即座に測定します。

1Type or paste your password into the input field.
2Toggle the eye icon to show or hide the password characters.
3Check the visual strength bar and score (0-100) for an instant assessment.
4Review the criteria checklist to see exactly which requirements your password meets.
5Use the entropy value and estimated crack time to gauge real-world security.

主な機能

Real-time strength scoring with 9-point criteria checklist
Entropy calculation and estimated crack time at 10B guesses/sec
Detects common patterns, dictionary words, and repeated sequences
100% client-side — your password never leaves your browser

よくある質問

詳しく読む

How to Check If Your Password Is Actually Strong