Password GeneratorFree online other calculator — instant results, no sign-up
Create a strong random password.
About the Password Generator
This calculator generates cryptographically secure random passwords and estimates their theoretical information entropy. It is designed for individuals and system administrators seeking strong credentials resistant to automated brute-force attacks.
- Length
- Number of characters in the generated password, capped at a maximum of 128
- Include symbols
- Whether to include 15 standard punctuation characters alongside alphanumeric characters (Yes or No)
Formula and method
Entropy (bits) = L × log2(N)
- EntropyTheoretical password strength measured in bits
- LPassword length (clamped to a maximum of 128 characters)
- NCharacter pool size (72 when symbols are included, 57 when excluded)
The generator builds a pool of characters that omits visually ambiguous characters (uppercase I, O; lowercase l; and digits 0, 1). Using browser-native Web Cryptography (crypto.getRandomValues), 32-bit unsigned integers are generated and mapped into the character pool via modulo indexing. Total entropy is calculated as length multiplied by the base-2 logarithm of the pool size, rounded to the nearest integer.
Worked example
These are the calculator's starting values and the results it actually produces for them.
Inputs
- Length16
- Include symbolsYes
Results
- Passworduo$^_GUm*h9fbHs%
- Entropy99 bits
How to use the Password Generator
- 1Determine the character pool size N (57 without symbols, 72 with symbols).
- 2Clamp the requested length L to a maximum value of 128 characters.
- 3Draw cryptographically secure random 32-bit values and select characters from the pool using modulo division.
- 4Calculate the total entropy as L × log2(N) and round to the nearest whole bit.
Reading your result
A higher bit value indicates greater resistance to exhaustive search attacks. Passwords with at least 80 bits of entropy are generally considered robust against online and offline dictionary attacks, while 100+ bits provide long-term resistance against high-speed hardware cracking.
Limitations
The algorithm selects each character independently at random, meaning it does not enforce guaranteed inclusion of at least one character from every subcategory. It caps maximum length at 128 characters, and the entropy metric assumes an attacker has no side-channel knowledge of the character pool constraints.
Common questions
Why are characters like 0, O, 1, and l excluded?+
They are omitted to prevent visual ambiguity and transcription errors when manually reading or typing passwords across different fonts and displays.
How is entropy calculated for passwords?+
Entropy measures the number of guesses required to crack a password in the worst-case scenario. It equals the password length multiplied by the base-2 logarithm of the character pool size.
Is the generated password truly random?+
Yes. It uses the browser's cryptographically secure pseudo-random number generator (CSPRNG via crypto.getRandomValues) rather than standard Math.random.
Does the calculator save my information?+
Calculations run in your browser. While signed in, inputs and results are automatically recorded in account history; saving a result creates a separate saved record.
Further reading
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Results are estimates for informational purposes and are not financial, medical or legal advice.