Passphrase Guide: Strength, Entropy, and Best Practices
Why four random words beat eight random characters, how to read the strength meter, and the habits that keep your accounts safe.
What is a passphrase?
A passphrase is a password made of several random words joined together. Pass makes ones like this:
Each extra word multiplies the number of possible passphrases. That makes a passphrase strong at a length you can still remember, say out loud and type on a phone.
Why length beats complexity
Strength is measured in bits of entropy. Each random choice adds bits. One random lowercase letter adds about 4.7 bits. One random word from a 1,296-word list adds about 10.3 bits. So one word is worth more than two random letters, and you can remember it.
P@ssw0rd! looks complex, but it is weak. It is short, and it follows a pattern that cracking tools try first. Length and real randomness make a password strong.
How strong is a passphrase?
Pass picks each word at random from a 1,296-word list. It capitalizes the first word and adds one random digit at the end. Each word adds about 10.3 bits. The meter adds 1 to 2.6 bits for the capital and 3.3 bits for the digit:
| Words | Entropy | Time to crack at 10,000 guesses a second |
|---|---|---|
| 3 + digit | ~37 bits | about 5 months |
| 4 + digit | ~47 bits | about 450 years |
| 5 + digit | ~57 bits | about 450,000 years |
| 6 + digit | ~67 bits | about 450 million years |
Four words (about 47 bits) is a good floor for everyday accounts. For email, banking and your password manager, use five or six words, which gives 57 bits or more. An attacker with a stolen password database can guess much faster than 10,000 a second. That is why the habits below matter more than a few extra bits.
Passphrase best practices
- Pick words at random. Words you like follow patterns that attackers guess. Pass uses your browser's crypto API, so no person picks the words.
- Use a different password for each account. If you reuse one, a breach at one site opens every account that shares it. A password manager remembers them for you.
- Protect your email first. Password resets go to your inbox, so give your email the longest passphrase and turn on two-factor authentication.
- Turn on two-factor authentication wherever a site offers it. It protects the account if a password leaks.
- Do not change a generated passphrase to make it easier to remember. If you swap in words you like, you remove the randomness that makes it strong.
- The site that stores your password decides how safe it is on their side. You control only your part, so make that part strong.
Frequently asked
Are passphrases better than passwords?
Yes, if the words are picked at random. Random words give you more strength for the same effort to remember, and length is what makes a password strong. Words you pick yourself are much weaker.
Is one digit enough?
The digit adds 3.3 bits, and it satisfies sites that ask for a number. The words give the strength. If you want more, add a word.
What if a site limits password length?
Use the longest password the site allows. Add whole words before you add symbols. Most sites accept 64 characters or more.
Make one now
Pass generates it in your browser with cryptographic randomness. It sends nothing anywhere.
Generate a passphrase →