Passphrases vs Random Passwords: Which Is Stronger?

By an independent developer · Updated October 11, 2026 · 8 min read

“Use a passphrase instead of a password” is common advice, usually illustrated with four random words. But is a passphrase actually stronger, and is four words enough? The answer depends on two numbers most articles leave out: how many words the phrase has, and how big the list they were drawn from is.

The two contenders

• Random password: characters chosen at random, e.g. r7#Kp!2vQz@m9W. Strong per character, hard to remember and type.
• Random passphrase: whole words chosen at random, e.g. Velvet-Orbit-Sample-Cradle-Unfold-Witness. Longer to type, far easier to remember.

Both are only strong when a computer (or dice) does the choosing. A phrase you invent — a song lyric, a quote, “correct horse battery staple” copied from a comic — is in attackers’ wordlists and phrase lists, however long it is.

The math, side by side

Each random character from the 88-character set used by our password generator adds about 6.46 bits. Each random word adds log₂ of the word-list size: about 11.0 bits for the 2,049-word list in our passphrase generator, and about 12.9 bits for the EFF’s 7,776-word Diceware list. (If entropy is new to you, start with password entropy explained.)

The table shows why “four random words” is not automatically strong. With a 2,049-word list it gives 44 bits, which a single GPU exhausts in about a minute against a fast unsalted hash. It is fine for an account protected by rate limiting, but not for anything that can be attacked offline. Six to seven words is where passphrases reach the same strength as a 12-character random password.

Does the word list size matter?

Yes, but less than the word count. Going from 2,049 words to 7,776 adds about 1.9 bits per word; adding one more word adds 11–13 bits. Larger lists also tend to include longer and less familiar words, which makes the phrase harder to remember and type. A reasonable rule: with a ~2,000-word list, use one more word than you would with a Diceware list.

What about capitals, numbers, and separators?

Capitalizing every word, or always using a hyphen, adds essentially nothing: the pattern is fixed, and the strength calculation already assumes the attacker knows your format. Randomly choosing whether each word is capitalized adds one bit per word — less than adding one more word to a 6-word phrase, and much harder to remember. If a site insists on a digit and a symbol, append them; just don’t count on them for strength.

When to use which

How to memorize a passphrase

• Build a picture. Link the words into a silly scene in order: the velvet orbit samples a cradle…
• Don’t edit it. Swapping a word for one you like better reintroduces human choice. Generate again instead.
• Practice with spacing. Type it several times over the first day, then once a day for a week. Keep a written copy in a secure place until it sticks.

Key takeaways

• Passphrases and random passwords are equally strong at equal entropy; the difference is memorability and length.
• Four words is not enough for anything that can be attacked offline. Use 6–7 words from a ~2,000-word list, or 6 from a Diceware list.
• Use random passwords for everything in your password manager, and a passphrase for the few secrets you must remember.

Sources

• EFF Dice-Generated Passphrases and the long word list
• NIST SP 800-63B-4 — guidance on length and accepting spaces in passwords (2025)