Passphrase generator
A passphrase is several random words in a row, such as zipping-cactus-tidy-ladle-wobble. It is easier to type and remember than a string of symbols. This tool picks the words with your browser's cryptographic random generator and shows how many bits of entropy the result has.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- Choose how many words you want. Five or six is a common choice for an account you must type by hand.
- Pick a separator, and optionally capitalise the words or add a digit if a site demands it.
- Press New passphrase, check the entropy, and copy it into your password manager or learn it.
How the entropy is worked out
With a list of 7,776 words, one word has log2(7776) ≈ 12.925 bits of entropy.
| Words |
Entropy |
| 4 |
51.7 bits |
| 5 |
64.6 bits |
| 6 |
77.6 bits |
| 7 |
90.5 bits |
The figure assumes an attacker knows the list and the method but not the words you got. If you keep pressing the button until you like the phrase, you lower the real entropy, so use the first one or accept the loss.
Tips
- Do not swap a word you dislike for one of your own: that undoes the randomness.
- A passphrase is as strong as its entropy, not as its length in letters.
- Never reuse a passphrase on two accounts.
Word list credit
Word list: EFF large wordlist, by the Electronic Frontier Foundation, licensed under CC BY 3.0 US. Source: eff.org, “Deep Dive: EFF’s New Wordlists for Random Passphrases” (2016).
Frequently asked questions
How is the entropy calculated?
Every word is chosen independently and with equal probability from a list of 7,776 words, so each word adds log2(7776) ≈ 12.9 bits. Five words give about 64.6 bits, six about 77.5. A digit at the end adds log2(10) ≈ 3.3 bits. Capital letters and the separator are fixed by your choice, so they add nothing.
Is a passphrase better than a password?
For a password you have to type or remember, a passphrase of random words gives good entropy with something you can actually recall. For a password stored in a password manager, a long random password works just as well. What matters is that the words are chosen at random, not picked by you.
Where does the word list come from?
It is the EFF large wordlist for dice, created by the Electronic Frontier Foundation and released under the Creative Commons Attribution 3.0 US licence. The words are used unchanged; only the dice numbers were removed.
Is the passphrase sent anywhere?
No. It is generated in your browser with crypto.getRandomValues and shown only on your screen. The page does not store or send it.