Make a passphrase of random words

Make a passphrase of random words

The words are made in your browser and never leave this page. The tool pages are served with a content security policy that forbids every network connection, so the page’s own script could not send a photo anywhere, not even back to this site. A check on every build fails if a tool script uses cookies, local storage, session storage or IndexedDB, so the photo tools keep nothing in your browser.

How many words 4 words 5 words 6 words 7 words 8 words 10 words

Between the words

A spaceEasiest to read and to type on a phone. A hyphenFor places that do not take spaces. A period

For sites with rules

Capitalize each wordFor a site that asks for a capital letter. It adds no strength, because every word gets one. Add one random digitFor a site that asks for a number. It goes in a random place and adds a few bits.

Each word is picked by your browser's cryptographic random number generator from a list of 7,775 words, every word equally likely. A new passphrase replaces the old one; the page keeps no list of them.

How the words are picked

1. Choose a length. Six words is the default, and the EFF’s advice for most uses. Choose more for something that guards a lot.
2. The browser draws each word. It uses crypto.getRandomValues, which gives cryptographically strong random values, and throws away the rare draws that would favour some words over others. Every word in the list is equally likely, every time.
3. Copy it, or make another. A new phrase replaces the last one. The page keeps no list, so a phrase you did not copy is gone.

Do not edit the phrase into something you like better. Swapping a word for a favourite one is a choice, and choices are what a guesser tries first.

What the bits mean

Bits of entropy count the guesses. Each bit doubles the number of phrases a guesser has to search. EFF’s long list has 7,776 words, so each word adds about 12.9 bits, and six words give about 77 bits. On average a guesser finds a phrase after trying half of all the combinations.

That count holds only for words picked at random. It already assumes the guesser has the same list and knows how many words you used. A phrase you make up yourself, such as a line from a song, is worth far less than its length suggests, because people pick lines that other people pick too.

Bits are not a time. How long a guess takes depends on what the phrase protects. A website that slows down wrong tries, or an app that stretches each guess with a slow key step, buys a lot of time. A file that someone can copy and test offline buys the least. Choose more words for that case.

How many words to choose

• 4 words, about 52 bits at 12.9 bits a word: fine where wrong tries are limited, such as a lock screen. Too short for anything that can be tested offline.
• 6 words, about 77 bits: the length the EFF suggests for most uses, and a sound default.
• Seven or more: for a password manager’s main password, or anything someone could copy and work on for years.

The word list, and the one word left out

The words are EFF’s long list for dice passphrases, published in 2016 and shared under a Creative Commons Attribution licence (the EFF’s copyright page names version 4.0, and its badge links the 3.0 US licence). Credit for the list belongs to the EFF. One word of its 7,776 is left out here: the verb meaning “go and get”. This site’s own check refuses that word in any script, because it is also the name of a call that sends data, and the check is what proves the tools send nothing. So this page draws from 7,775 words and counts the strength from that number, which costs a tiny fraction of a bit for each word.

Where Sealed helps, and where it doesn’t

It helps when you want a phrase in front of your vault key. With a vault passphrase, your vault key is sealed under a passphrase you type every time the vault unlocks, and if you lose it only your recovery key opens the vault. 12 characters A phrase of six words from this page clears that length easily. 1,000,000 rounds The vault passphrase is part of Sealed Pro.

It helps with a copy of your recovery key, too. Sealed suggests six random words as the phrase for a sealed copy, and you can type your own phrase instead. Sealed does not keep the phrase of a sealed copy, so a forgotten phrase means that copy can’t be opened.

It doesn’t keep your phrases for you. Because your key never reaches us, we cannot recover your vault or reset your passcode for you. Write a phrase down on paper, or keep it in a password manager, before you rely on it. The guide to choosing a passphrase covers where to keep one.