Passphrase Generator & Entropy Explorer
A good passphrase is one of the most effective security tools available — and one of the most underused. correct-horse-battery-staple is stronger than P@55w0rd! and infinitely easier to remember. This tool shows you exactly why.
Adjust the word count and dictionary size to see how entropy scales, generate a cryptographically secure passphrase from our curated wordlist, and compare it to an equivalent random password. Everything runs locally — no passphrases are transmitted or stored.
Why passphrases beat passwords
Traditional password advice — uppercase, numbers, symbols — produces passwords that are hard for humans to remember and easier for computers to crack than they look. The maths is counterintuitive.
Consider two passwords:
P@55w0rd!— looks complex, but variations on “password” are in every cracking dictionary. Effective entropy: near zero.correct horse battery staple— four random common words. Entropy: ~51 bits from a 7,776-word EFF list. Would take decades to crack even with a GPU cluster.
The difference: true randomness. A passphrase drawn from a large wordlist using a cryptographic RNG is unpredictable in a way that human-chosen “complex” passwords rarely are.
Understanding entropy
Entropy measures unpredictability in bits. Each bit doubles the number of possible values an attacker must search through.
For passphrases, entropy is: bits = word_count × log₂(dictionary_size)
With the EFF large wordlist (7,776 words):
- 3 words: 38.9 bits — crackable with sustained attack
- 4 words: 51.8 bits — strong for most purposes
- 5 words: 64.8 bits — exceeds NIST’s recommended minimum for high-value accounts
- 6 words: 77.5 bits — effectively uncrackable with current technology
The NIST recommendation
NIST Special Publication 800-63B (the US government’s digital identity guidelines) recommends at least 15 characters for memorised secrets, but entropy is a better measure than length alone. NIST explicitly endorses passphrases and recommends against mandatory complexity rules, which have long been shown to produce predictable patterns (for example Summer2026!) rather than genuine security.
Why the dictionary size matters so much
A 3-word passphrase from a 256-word dictionary has only 16.8 million combinations — crackable in under a second offline. The same 3 words from the EFF’s 7,776-word list has 470 billion combinations — still weak, but the difference is stark.
This is why “three random words” only works if the words are genuinely random and drawn from a large list. Choosing “cat dog house” is not random — an attacker targeting passphrases will try common words first.
What makes a good wordlist?
The EFF (Electronic Frontier Foundation) publishes a wordlist specifically designed for passphrase generation. Each word is:
- Common enough to be memorable
- Long enough to resist single-word guessing
- Unambiguous when read aloud
- Free of offensive or confusing terms
The words in this tool are drawn from a similar curated set. For the highest security, use 5+ words from the largest dictionary option.
Passphrase vs password — which should I use?
| Scenario | Best choice |
|---|---|
| Master password / password manager | Passphrase (5+ words) |
| Account you type manually and often | Passphrase (4+ words) |
| Generated for a password manager | Random password (20+ chars) |
| Wi-Fi password shared with others | Passphrase (easier to communicate) |
| System administrator access | Passphrase (5+ words) + MFA |
The honest answer: for anything you need to type from memory, a passphrase is almost always the better choice. For everything else, use a password manager with randomly generated passwords.