OneTaskBy Tim King · Updated
Passphrase Generator
Diceware Passphrases from the EFF Wordlist, with Word Count and Separator Options
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How the Passphrase Generator works
This passphrase generator strings random words into a strong password. Pick how many words you want and a separator, and the generator draws them at random from the EFF long wordlist of 7,776 English words using your browser's cryptographic random source. The entropy and time to crack update with every setting. Everything is generated locally and never sent anywhere; the wordlist is built into the page.
Passphrase generator: why words beat characters
A password like Tr0ub4dor&3 is hard for a person to remember and easy for a computer to guess,
because its tricks — a capital at the front, digits for letters, a symbol at the end — are the
first substitutions any cracking tool tries. A passphrase of five random words is the reverse:
correct horse battery staple is something you can carry in your head after a few uses, and
its strength comes from the number of possible combinations rather than from obscurity. The
only requirement is that the words are chosen at random. A phrase you make up yourself, from a
song lyric or a sentence, is drawn from a far smaller space than it appears.
How diceware works
Diceware, published by Arnold Reinhold in 1995, chooses each word by rolling five dice and
looking up the result in a list of 6⁵ = 7,776 words. This page uses the Electronic Frontier
Foundation's 2016 long wordlist, which was rebuilt for the same purpose with words that are
easier to spell, recognisable, and free of the obscure or offensive entries the original
contained. The dice are replaced by crypto.getRandomValues, with rejection sampling so every
word is exactly equally likely.
How many words in a passphrase
Each word from a 7,776-word list adds log₂(7776) ≈ 12.9 bits of entropy. The table shows what that gives at each length, with the offline crack time at ten billion guesses per second — a capable password-cracking rig against a fast hash.
| Words | Entropy | Combinations | Offline crack time |
|---|---|---|---|
| 3 | 39 bits | 4.7 × 10¹¹ | about 24 seconds |
| 4 | 52 bits | 3.7 × 10¹⁵ | about 2 days |
| 5 | 65 bits | 2.8 × 10¹⁹ | about 45 years |
| 6 | 78 bits | 2.2 × 10²³ | about 350,000 years |
| 7 | 90 bits | 1.7 × 10²⁷ | about 2.7 billion years |
| 8 | 103 bits | 1.3 × 10³¹ | longer than the age of the universe |
Four words is adequate for anything behind a rate limit. Six is the usual recommendation for a master password, disk encryption or a cryptocurrency seed, where an attacker gets an offline copy and unlimited attempts.
Separators, capitals and numbers
The separator does not add meaningful entropy, since an attacker can try each one, but it matters for usability: hyphens survive being read aloud, spaces are rejected by some old forms, and none makes the phrase harder to read. Capitalising each word and appending a number are for sites whose rules demand a capital and a digit; the two-digit number adds about 6.6 bits, the capitals add none because they are predictable. If a site needs a symbol, use the hyphen separator.
Generated locally, never sent
The wordlist and the generator are part of the page. No request leaves your browser when you generate, nothing is logged, and closing the tab removes every trace. Regenerate until you get a phrase you like — rejecting phrases does not weaken the result — then store it in a password manager, or write it down and keep the paper somewhere a stranger cannot reach.
FAQ
Is a passphrase really stronger than a random password?
Bit for bit, no: a 12-character random password from 94 symbols has 79 bits, about the same as six words. The difference is that you can remember six words and you cannot remember twelve random symbols, so in practice the passphrase is the one that ends up longer and not reused.
How many words should I use?
Four for ordinary accounts protected by a login rate limit, six for anything an attacker could copy and crack offline, such as a password manager master password, full-disk encryption or a wallet seed. Seven or more is for long-term secrets you expect to protect for decades.
Can I change a word I don't like?
Yes, regenerate until the phrase suits you. Discarding phrases does not reduce the entropy of the one you keep, because each is drawn independently. What does weaken it is editing words by hand into something meaningful, which drops the phrase into the space of things people would guess.
Why is the wordlist 7,776 words?
Because the original diceware method chose words by rolling five six-sided dice, and 6⁵ is 7,776. The EFF kept that size for compatibility with physical dice, and it gives 12.9 bits per word. Larger lists exist but push into obscure words that are harder to spell.
Is it safe to generate a passphrase on a website?
On this one, yes, because the wordlist is embedded in the page and the words are drawn in your browser with the same cryptographic generator the operating system uses. Nothing is transmitted. The same cannot be assumed of every generator, so check that the page works with the network disconnected.
See also: all Security & Identifiers tools, Dev Utilities, Formatters & Validators, Data & Encoding, SEO, Accessibility, AI.
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