Diceware Passphrase Generator

Why a few random words beat a complicated password

A passphrase is a password made of several random words — willow-cobalt-meadow-quartz instead of X7#kq!2P. It feels less "secure" because it is readable, but that intuition is backwards. Passphrases can carry just as much entropy as symbol soup while being dramatically easier to remember and to type, which is exactly why security researchers and the EFF recommend them.

The Diceware idea, automated

The technique behind this generator is Diceware, devised by Arnold Reinhold. The original method has you roll physical dice to choose words from a numbered list, so the selection is provably random and free of human bias. We replace the dice with crypto.getRandomValues(), the browser's cryptographically secure random number generator, drawing each word independently and uniformly from the list.

Where the entropy comes from

The strength of a passphrase is governed by one formula: words × log2(list size). Critically, the entropy depends on the size of the list and how many words you pick — not on the specific words that appear. Here is how that scales for a representative word list:

Per word from a 100-word list:   log2(100)  ≈ 6.6 bits
Per word from a 7,776-word list: log2(7776) ≈ 12.9 bits

4 words from a large list:  4 × 12.9 ≈ 52 bits
5 words from a large list:  5 × 12.9 ≈ 64 bits
6 words from a large list:  6 × 12.9 ≈ 77 bits

The live entropy readout in the tool reflects this same math for the built-in list, so you can watch strength climb with every word you add.

A public word list is not a weakness

It can feel wrong that the word list is openly known, but that is by design. Real cryptographic security follows Kerckhoffs's principle: a system should stay secure even when everything about it except the key is public. Here the "key" is the random choice of words. An attacker who knows the entire list still has to contend with the full set of equally likely combinations — a secret list would add no protection at all.

Choosing a length that fits the job

• 4 words — fine for low-value, throwaway logins.
• 5 words — a strong, comfortable everyday default.
• 6+ words — for a password-manager master password or anything that, if breached, unlocks everything else.

Adding a word multiplies the attacker's effort far more than sprinkling in symbols does, so when in doubt, lengthen the phrase rather than complicate it.

Related security tools

• Password Generator — when an account wants a random character string rather than words.
• Password Strength Checker — type a phrase in to see the word count translate into bits of entropy.
• OTP Generator — add a time-based second factor on top of the account this passphrase protects.