Passphrase Generator

A passphrase of several random words is both easy to remember and very hard to guess — the approach made famous by the "correct horse battery staple" comic. This generator picks words from a built-in list using the browser’s secure random source and reports the exact entropy, so you can see how strong each passphrase really is.

How to use this tool

1. Choose how many words per passphrase (seven or more is recommended with this list).
2. Set how many to generate and the separator.
3. Optionally capitalise words or add a digit or symbol.
4. Generate and copy a passphrase you like.

Formula

Entropy = number of words × log₂(word-list size). With this 815-word list each word adds log₂(815) ≈ 9.67 bits, so seven words give about 67.7 bits. A digit at the end adds log₂(10) ≈ 3.3 bits and a symbol log₂(13) ≈ 3.7 bits.

This assumes an attacker knows the word list and that the words are chosen uniformly at random, which this tool ensures.

Example

A seven-word passphrase from this 815-word list carries about 67.7 bits of entropy: at 10 billion guesses a second, trying half of the possibilities would take around 380 years. Five words (48.4 bits) would fall in about five hours, which is why this tool starts at seven.