What Makes a Strong Password?
A strong password has three properties: sufficient length, diverse character types, and true randomness. Length is the most important factor. Each additional character exponentially increases the number of combinations an attacker must try. A 16-character random password is billions of times harder to crack than an 8-character one, even with the same character set.
Character diversity matters because it expands the pool of possibilities for each position. Using uppercase letters, lowercase letters, digits, and symbols gives a character set of 94, compared to 26 for lowercase only. But a 20-character lowercase-only password is still stronger than an 8-character password using all character types.
Password Entropy Explained
Entropy measures the unpredictability of a password in bits. The formula is: entropy = length x log2(charset_size). A password with 40 bits of entropy is weak (crackable in minutes), 60 bits is fair, 80 bits is strong, and 100+ bits is very strong. This tool shows the entropy of each generated password so you can make informed decisions.
Human-chosen passwords have much lower effective entropy than their length suggests because humans use predictable patterns: dictionary words, names, dates, keyboard sequences, and common substitutions (@ for a, 3 for e). Attackers exploit these patterns with dictionary attacks and rule-based cracking tools like Hashcat and John the Ripper.
How This Generator Works
This tool uses the Web Crypto API (crypto.getRandomValues), which draws randomness from your operating system's cryptographic entropy source. This is the same source used for TLS keys and other security-critical operations. The password is generated entirely in your browser. No data is sent to any server, and nothing is stored.
How to Use This Generator
- Set your desired password length (default is 16 characters; 12 minimum recommended).
- Select which character types to include: uppercase (A-Z), lowercase (a-z), digits (0-9), and/or symbols (!@#$%).
- Click Generate for a single password, or Generate 10 for a batch to choose from.
- Click the password or the Copy button to copy it to your clipboard.
Frequently Asked Questions
How long should a password be?
Security experts recommend a minimum of 12 characters, with 16 or more being ideal. Each additional character exponentially increases the number of possible combinations an attacker must try. A 16-character password with mixed character types has over 10^30 possible combinations, making brute-force attacks infeasible with current technology.
What is password entropy?
Password entropy measures the unpredictability of a password in bits. It is calculated as length multiplied by log2 of the character set size. A password with 80+ bits of entropy is considered strong. For example, a 16-character password using uppercase, lowercase, digits, and symbols (94 characters) has about 105 bits of entropy.
Are random passwords really more secure?
Yes. Human-chosen passwords follow predictable patterns (dictionary words, dates, keyboard sequences) that attackers exploit with dictionary attacks and rule-based cracking. Truly random passwords have no patterns to exploit, forcing attackers to try every possible combination (brute force), which is vastly slower.
Should I use special characters?
Including special characters increases the character set size from 62 (letters + digits) to 94+, which significantly increases entropy per character. However, length matters more than complexity. A 20-character password of only lowercase letters is stronger than an 8-character password with all character types. Use special characters when possible, but prioritize length.
How does a password generator work?
This generator uses the Web Crypto API (crypto.getRandomValues), which provides cryptographically secure random numbers from the operating system's entropy source. For each character position, it generates a random index into the selected character set and picks the character at that position. The result is a password with no predictable patterns.
Is it safe to generate passwords online?
It is safe when the generator runs entirely in your browser with no server communication, as this one does. The password is generated using your browser's built-in Crypto API and never leaves your device. No data is sent to any server. You can verify this by checking the network tab in your browser's developer tools.