Generate a strong password

This generator makes random passwords, word passphrases and BIP39-format phrases, and shows how strong each one is in bits of entropy. Everything is generated in your browser with its cryptographic random generator (crypto.getRandomValues). Nothing is sent, nothing is saved.

Three kinds of secret

How to use it

1. Choose Password, Passphrase or BIP39 phrase.
2. Adjust the options: length and character types, or number of words and separator. A new value appears with every change.
3. Tap Copy and paste it where it belongs, or Generate again for another.

The strength bar and the entropy figure update with every option, along with how long an attacker would need on average at ten billion guesses a second, a fast offline attack on a leaked password database.

How the entropy is calculated

Entropy counts how many equally likely results the generator could produce, in powers of two.

• Passwords draw each character uniformly from the sets you pick (26 lowercase, 26 uppercase, 10 digits, 28 symbols). The generator guarantees at least one character from every chosen set, and the figure shown accounts for that rule exactly instead of rounding up. "Avoid look-alikes" removes O, 0, o, I, l, 1 and | for codes you need to read aloud or copy by hand.
• Passphrases pick each word uniformly from the 2048-word BIP39 English list, so every word adds 11 bits: 6 words give 66 bits, 8 words give 88. Capitalizing doesn't add entropy here, since it is applied to every word; adding a digit adds a few bits.
• BIP39 phrases encode 128 bits (12 words) or 256 bits (24 words) of fresh randomness, plus a checksum taken from SHA-256, as the BIP39 standard defines.

Every random choice is made with rejection sampling, so no character or word is slightly more likely than another.

How strong is strong enough?

• Under 50 bits: fine for a code that changes often, weak for anything an attacker can test offline.
• 50–80 bits: reasonable for online accounts that limit login attempts.
• 80–110 bits: strong against offline guessing with today's hardware.
• Over 110 bits: more than enough for nearly anything.

A password manager plus one strong passphrase to open it covers most people. Turn on two-factor authentication where you can: it protects you when a site leaks your password, however long it is.

About the BIP39 mode

The BIP39 English wordlist is the 2048-word list used by many recovery phrases. It is public and published under the MIT License; we serve a copy from this site, so the page works offline.

The phrase you get here is random and has a valid checksum, so tools that check the format will accept it. That doesn't make this page a good place to create a crypto wallet. For keys that protect money, let the wallet generate its phrase on its own device, write it on paper, and never type it into a website. Our guide on storing a crypto seed phrase safely covers the options, and what a recovery phrase is explains how they work.

Passwords, PINs and signs

Long random secrets are excellent for things you paste. They are tiring for things you unlock fifty times a day. That is why phones use PINs and patterns, and why the trade-offs are worth knowing: our comparison of pattern lock vs. PIN vs. password goes through them.

sigil. takes a different route for photos. A vault opens with a sign you draw on a 5×5 grid, run through Argon2id and tied to the phone's secure chip, so it can't be guessed away from the device. Its recovery phrase is created by the app on your phone when you set it up, not on this page, and it is the only way back in if you forget your sign. Nobody can reset it for you, not even us.