Free Password Generator & Strength Checker

Generate cryptographically secure random passwords and test password strength with real-time entropy analysis. 100% free, no signup, fully private — powered by the Web Crypto API and NIST SP 800-63B guidelines.

100% Private
NIST Compliant
Instant Generation
No Signup Required

Updated on: October 14, 2026 · References: NIST SP 800-63B, OWASP Password Guidelines, Shannon Information Theory

Password Strength

Very Weak

Can be cracked in seconds

Score

0/100

Entropy

0 bits

Crack Time

Instantly

Password Settings

16
43264128
A-ZUppercase letters
a-zLowercase letters
0-9Numbers
!@#Symbols
Exclude ambiguous (il1Lo0O)
Custom exclude
Quantity1

Key Features

Built with security best practices following NIST guidelines and modern cryptographic standards

Cryptographically Secure

Uses the Web Crypto API (crypto.getRandomValues) for true randomness — the same standard used by banking and government systems per NIST SP 800-90A.

Real-Time Strength Analysis

Instantly evaluates entropy, character diversity, and pattern detection based on NIST SP 800-63B Digital Identity Guidelines.

100% Client-Side Processing

Your passwords never leave your browser. Zero server requests, zero data storage. Fully GDPR and privacy compliant by design.

Highly Customizable

Fine-tune length (4–128 chars), character types, ambiguous character exclusion, and custom exclusion sets for any password policy.

Bulk Generation & Export

Generate up to 50 passwords at once. Copy individually, copy all, or download as a .txt file for password manager imports.

Crack Time Estimation

Estimates time-to-crack against a 10 billion guesses/second attack model (modern GPU cluster), giving real-world security context.

Entropy Calculation

Displays Shannon entropy in bits — the gold standard metric used by security professionals to quantify password unpredictability.

No Signup, No Ads, 100% Free

Completely free to use with no account required. No ads, no tracking, no limitations. Open to everyone, everywhere.

What Is a Password Generator?

A password generator is a software tool that creates random, unpredictable passwords using cryptographically secure algorithms. Unlike human-chosen passwords, generated passwords have maximum entropy — the measure of randomness defined by information theory (Shannon, 1948). According to NIST Special Publication 800-63B, passwords should be at least 8 characters, but security experts recommend 16+ characters with mixed character types for optimal protection against brute-force and dictionary attacks.

Why Strong Passwords Matter in 2025

According to the Verizon 2024 Data Breach Investigations Report, over 80% of hacking-related breaches involve stolen or weak credentials. Modern GPU clusters can test 10 billion password combinations per second, making short or predictable passwords dangerously vulnerable.

❌ Weak Password Examples

  • • password123 — cracked instantly
  • • John1990! — personal info, predictable
  • • qwerty — keyboard pattern
  • • Summer2024! — seasonal + year pattern

✅ Strong Password Characteristics

  • • 16+ characters in length
  • • Mix of upper, lower, numbers, symbols
  • • No dictionary words or personal info
  • • Generated with CSPRNG (crypto.getRandomValues)

How Password Entropy Works

Entropy measures password strength in bits. The formula is: E = L × log₂(R) where L is length and R is the character pool size. A 16-character password using all character types (94 possible characters) has approximately 105 bits of entropy — requiring 2¹⁰⁵ guesses to guarantee cracking.

Entropy Reference Table (NIST Guidelines)

Entropy (bits)StrengthCrack Time (10B guesses/sec)
28Very Weak~27 seconds
36Weak~2 hours
60Moderate~36 years
80Strong~38 million years
128+Very StrongBillions of years

How to Use This Password Generator

1

Set Password Length

Use the slider to select your desired password length (4–128 characters). NIST recommends at least 8 characters; we recommend 16+.

2

Choose Character Types

Toggle uppercase, lowercase, numbers, and symbols. More character types = higher entropy = stronger passwords.

3

Configure Advanced Options

Optionally exclude ambiguous characters (il1Lo0O) or add custom exclusions to match your system's password policy.

4

Generate & Review

Click "Generate Password" to create cryptographically random passwords. Review the strength meter, entropy, and estimated crack time.

5

Copy or Download

Copy individual passwords to clipboard or download bulk passwords as a .txt file. Store securely in a password manager.

🔬 Technical Transparency & Trust

  • • Random Number Generation: Uses crypto.getRandomValues() — a CSPRNG compliant with NIST SP 800-90A
  • • Strength Assessment: Based on NIST SP 800-63B Digital Identity Guidelines (Rev. 4, 2024)
  • • No Server Communication: All processing runs in-browser via JavaScript/WebAssembly — verifiable via browser DevTools Network tab
  • • Open Standards: Entropy calculation follows Shannon's information theory (1948)
  • • Last Updated: February 2025 — aligned with current NIST and OWASP recommendations

Frequently Asked Questions

Expert answers about password security, generation, and best practices

Yes — 100% free, no account required, no ads, and no usage limits. Our free password generator runs entirely in your browser using the Web Crypto API, so there is nothing to sign up for.

We use crypto.getRandomValues(), a Cryptographically Secure Pseudo-Random Number Generator (CSPRNG) built into every modern browser. This is the same standard recommended by NIST SP 800-90A and used by banking and government applications for generating unpredictable random values.

Absolutely not. Both the password generator and the password strength checker operate 100% client-side in your browser. No passwords, no keystrokes, and no analytics data ever leave your device. You can verify this by checking the Network tab in your browser's DevTools.

According to NIST SP 800-63B (2024 revision) and OWASP guidelines: use at least 16 characters, include uppercase, lowercase, numbers, and symbols. Avoid dictionary words, personal information, and sequential patterns. Our generator creates passwords with 80–128+ bits of entropy, which would take billions of years to crack.

Password strength is measured using Shannon entropy (bits), which quantifies the unpredictability of a password. The formula is E = L × log₂(R), where L is the password length and R is the character pool size. We also check for repeating characters, sequential patterns, and character diversity. A score of 80+ bits of entropy is considered strong.

Crack time estimates how long it would take an attacker with a modern GPU cluster (testing ~10 billion passwords per second) to brute-force your password. A 16-character password with all character types would take millions of years to crack — making it effectively unbreakable with current technology.

Yes! Use the quantity slider to generate up to 50 passwords simultaneously. You can copy all of them at once or download them as a .txt file for bulk import into password managers like 1Password, Bitwarden, or KeePass.

Both are valid approaches. NIST SP 800-63B actually recommends allowing passphrases (long sequences of random words). A 4-word passphrase from a 7,776-word list (Diceware) provides ~51 bits of entropy. For maximum security, a 16+ character random password with all character types provides 100+ bits of entropy. Use a password manager to store either type.

Ambiguous characters are visually similar characters like i, l, 1, L, o, 0, O. Excluding them prevents confusion when manually typing passwords (e.g., for WiFi passwords or shared credentials). This option slightly reduces entropy but improves usability for passwords that need to be read and typed.

NIST SP 800-63B (2024) no longer recommends periodic password changes unless there's evidence of compromise. Instead, focus on: unique passwords for every account, using a password manager, enabling multi-factor authentication (MFA), and monitoring for breached credentials via services like Have I Been Pwned.

Create strong, random, secure passwords instantly. Adjustable length up to 64 chars, symbols, numbers, and passphrases.

Tool
Strong Password Generator
Category
All tools
Availability
Browser-based tool