What makes a password secure?

A secure password should be at least 12 characters long and include uppercase and lowercase letters, digits, and special characters. Avoid using easily guessable information like birthdays or phone numbers. This tool evaluates password strength based on these rules.

How long would it take to crack a password?

It depends on password complexity and attack method. An 8-digit numeric password could be brute-forced in seconds, while a 16-character mixed password could take tens of thousands of years. It's recommended to change important account passwords regularly.

🔐 Password Strength Checker

Evaluate password security and get improvement suggestions

Password Length

Lowercase (a-z)26 chars

Uppercase (A-Z)26 chars

Digits (0-9)10 chars

Symbols (!@#$...)32 chars

Password Strength

Strong

Entropy 71.5 bits

Pool Size

Combinations

3.23e+21

Entropy

71.5 bits

Brute Force Time

10 thousand years

Strength Levels

Very Weak (<28 bits) — Instant crack

Weak (28-36 bits) — Minutes to crack

Medium (36-60 bits) — Days to years

Strong (60-80 bits) — Years to millennia

Very Strong (>80 bits) — Practically unbreakable

* Assuming an attacker tries 10 billion (10^10) attempts per second

Password Generator Guide

This tool generates secure random passwords. You can customize password length and character types (uppercase, lowercase, numbers, special characters).

Strong passwords are the first line of defense for account security. Use a different password for each account.

Password Security Tips

Password strength assessment:

- Weak: 6-digit numbers only, crack time < 1 second - Medium: 8 characters (letters + numbers), crack time: hours - Strong: 12 characters (mixed), crack time: centuries - Very strong: 16+ characters (mixed), crack time: millennia

Security recommendations: 1. Minimum 12 characters 2. Include uppercase, lowercase, numbers, and special characters 3. Don't use personal info (birthdays, phone numbers) 4. Different password for each account 5. Change important account passwords regularly 6. Enable two-factor authentication (2FA)

FAQ

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Password Strength Checker Guide

The Password Strength Checker evaluates password security by analyzing password length and character set combinations. Select the password length and enabled character types (uppercase, lowercase, digits, special symbols), and the tool calculates the character pool size, possible combinations, information entropy, and theoretical brute force cracking time.

Information entropy is the core metric for measuring password strength — the higher the entropy, the more secure the password. This tool assumes an attacker's brute force speed of 10 billion (10^10) attempts per second to estimate cracking time, helping users intuitively understand the security differences between different password configurations.

Password Strength Formulas

【Pool Size】N = Sum of enabled character set sizes
Lowercase 26 + Uppercase 26 + Digits 10 + Symbols 32 = 94 (all enabled)

【Combinations】Combinations = N^length
【Entropy】Entropy = log₂(N^length) = length × log₂(N) (unit: bits)

【Crack Time】Time = N^length / 10^10 seconds

【Strength Level Standards】
<28 bits: Very Weak | 28-36 bits: Weak
36-60 bits: Medium | 60-80 bits: Strong
>80 bits: Very Strong

Practical Examples

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【Example 1】8-digit numeric password Length=8, digits only (10 characters) Combinations = 10^8 = 100 million Entropy = 8 × log₂(10) ≈ 26.6 bits → Very Weak Crack time: ~0.01 seconds 【Example 2】12-character mixed password (upper+lower+digits) Length=12, pool=62 Combinations = 62^12 ≈ 3.23×10^21 Entropy = 12 × log₂(62) ≈ 71.5 bits → Strong Crack time: ~10 years 【Example 3】16-character all-types password Length=16, pool=94 Combinations = 94^16 ≈ 4.27×10^31 Entropy = 16 × log₂(94) ≈ 105.1 bits → Very Strong Crack time: Billions of years+

Important Notes

💡

- Password length matters more than complexity — 16 pure letters are stronger than 8 mixed characters - Avoid using personal information (birthdays, names, phone numbers) as password components - Use different passwords for different accounts; avoid "one password for everything" - It's recommended to use a password manager to generate and store high-strength random passwords - Change important account passwords regularly (recommended every 3-6 months) - Enabling two-factor authentication (2FA) significantly improves account security

Application Scenarios

- Personal accounts: Evaluate password security for social media, email, online banking, etc.
- Enterprise security: Set minimum password policy requirements for internal systems
- Compliance auditing: Meet GDPR, ISO 27001, and other security compliance requirements
- Security education: Help non-technical users understand the importance of password security
- Development testing: Verify whether password strength validation logic is reasonable

Password Security Best Practices

Beyond increasing length and complexity, modern password security also requires attention to: (1) Using passphrases instead of traditional passwords — e.g. "Correct-Horse-Battery-Staple" is both memorable and long; (2) Using a unique password for each website, paired with a password manager (such as Bitwarden, 1Password); (3) Enabling two-step verification for critical accounts; (4) Being alert to phishing attacks — even the strongest password is powerless against phishing.

NIST's latest guidelines (SP 800-63B) recommend no longer mandating periodic password changes, and instead encouraging long passphrases and password managers. Frequent password changes actually lead users to choose weaker, patterned passwords.

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