Passphrase Generator (Diceware)

How to use this tool

1. Choose word count. Drag the slider to set the number of words. Six words is a good default; add more for very high-value accounts.
2. Pick a wordlist. The EFF Long list has 7776 words (12.9 bits each); EFF Short has 1296 (10.3 bits each). Long gives higher entropy per word.
3. Configure extras. Optionally add a digit or symbol for sites that require them. Choose lowercase, first-letter, all-caps, or random first-letter capitalization.
4. Generate. Click Generate. The passphrase and its constituent words appear below. Click Copy to put it on your clipboard.

What is Diceware?

Diceware is a passphrase generation method invented by Arnold Reinhold in 1995. The original technique uses five physical six-sided dice: rolling them once produces a five-digit number (e.g., 34152) which maps to a single word in a numbered wordlist of exactly 7776 entries. Repeating the process for each word in the passphrase gives a result with mathematically verifiable randomness. No computer required.

This tool replaces the physical dice with crypto.getRandomValues, the browser's CSPRNG. The result has equivalent statistical properties: each word is drawn uniformly from the wordlist, and each draw is independent. Base entropy is log₂(wordlist size) × word count; an enabled digit or symbol adds its own selection entropy. The estimate does not depend on the specific words chosen, and it does not credit separators or capitalization.

EFF wordlists

In 2016, the Electronic Frontier Foundation published revised Diceware wordlists designed for better memorability. Their long list (7776 words, matching the original five-dice format) replaces obscure terms and ambiguous words with common, concrete English vocabulary. Their short list (1296 words, four-dice format, 10.3 bits per word) is better suited to mobile typing where shorter words matter more. The EFF wordlists are licensed under Creative Commons Attribution 3.0 (CC BY 3.0).

List attribution: Electronic Frontier Foundation (EFF), EFF Long wordlist and EFF Short wordlist 1, licensed under Creative Commons Attribution 3.0 (CC BY 3.0).

How many words is enough?

At 5 words, EFF Long provides about 64.6 bits of entropy. A simplified offline attack at one billion guesses per second would take an average of about 450 years to find the phrase. At 6 words (about 77.5 bits), that same rate gives an average search of about 3.5 million years. These are estimates, not guarantees: actual risk depends on the attacker, password storage, and account protections. Consider a 7th word for encryption keys or other high-value secrets.

Passphrases versus passwords

A 6-word EFF Long passphrase has about 77.5 bits of entropy, comparable to a uniformly random 13-character password drawn from 62 uppercase letters, lowercase letters, and digits. The passphrase is longer but often easier to memorize and type. For a password manager you type once per device, use a passphrase. For service accounts you manage programmatically and never type, use the random-character generator.

Entropy reference table

These times use half of the possible passphrases as the expected number of guesses in a uniform search. They describe an offline attack at the stated rate; real attackers, hash speeds, and hardware vary. Online login systems with rate limiting make guesses much slower.

Memorization techniques

The most effective method for remembering a passphrase is the story method: create a vivid, unusual mental narrative connecting your 5–6 words in sequence. The more bizarre and emotionally vivid the story, the more memorable it is.

Example passphrase: correct horse battery staple (the classic XKCD 936 example) -> visualize a horse riding a bicycle while wearing a correct school tie, carrying a battery that is stapled to a sign. The absurdity makes it stick. For links to mnemonic tools, see the Mnemonic Generator.

When NOT to use a passphrase

Some systems impose short maximum password lengths (16 or 20 characters is common, especially on older banking sites). A 6-word EFF passphrase averages about 30 characters and will be rejected by these systems.

In those cases, use a random character-based password generator and store the result in a password manager. Never truncate a passphrase to fit a length limit - a 4-word passphrase trimmed to 16 characters loses predictable entropy.