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Passphrase or password: which should you actually use?

14 Oct 2026 · Security · 7 min read

You need a new password, and you have two philosophies to choose from. One says: a short string of random characters, something like k7#Rv2mQ!pLz9Wt@fHn4, generated by a machine and stored in a password manager. The other says: several real words in a row, like correct-horse-battery-staple, long but made of ordinary English, something a human might actually remember.

Both camps have passionate defenders, and both will tell you the other approach is broken. The truth is more boring and more useful: they are two different answers to two different questions. A password and a passphrase optimise for different things, and the right choice depends on what you're protecting and how you'll use the secret day to day.

This article walks through both honestly: what each one is, how their strength actually compares when you do the maths, where human memory fits in, and a simple rule for picking between them that you can apply in about ten seconds.

What each one actually is

A password, in the modern sense, is a relatively short string drawn randomly from a large character set: uppercase letters, lowercase letters, digits and symbols. A 16-character password from the full 94 printable ASCII characters is the classic example. Nobody invents it — a generator makes it, and a password manager remembers it, because no human is going to memorise xQ9$mK2!vLz#pR4&wN and type it correctly twice.

A passphrase is a sequence of ordinary words picked at random from a fixed list: fabric-ideal-sandy-wander-movie. The words are real, which makes the result pronounceable and chunkable by human memory. The randomness matters just as much here as it does for passwords — the words must be chosen by a random process, not picked by you. A human choosing "clever" words produces something far more predictable than they feel it is, which defeats the entire purpose.

The key insight is that both are just ways of encoding randomness. A password packs a lot of randomness into few characters; a passphrase spreads the same amount of randomness across more characters that happen to be readable. Neither is magic. Both live or die on the quality of the random generation behind them.

The strength comparison, with the maths shown

Strength here means entropy: the number of possibilities an attacker would have to search, assuming they know exactly how your secret was made. Let's compute both properly.

Take a password of 16 characters drawn from 94 possible characters. Each character carries log₂(94) ≈ 6.55 bits of entropy, so the whole password carries about 105 bits. That's roughly 4 × 10³¹ possibilities.

Now take a passphrase of 7 words drawn from a list of 2,048 words. Each word carries log₂(2048) = 11 bits, so seven words give 77 bits — about 1.5 × 10²³ possibilities. A 5-word passphrase from the same list gives 55 bits.

Here's a side-by-side comparison with realistic crack times, assuming an attacker can try 10 billion guesses per second (a fast but plausible rate for offline attacks against a stolen hash file):

Two things stand out. First, a 5-word passphrase at 55 bits is genuinely weaker than a 12-character password at 79 bits — the famous "four words is enough" advice from a decade ago assumed slower attackers and smaller threat models than many people face today. Second, length scales beautifully for passphrases: each extra word adds a full 11 bits, so going from 5 words to 8 words multiplies the search space by over two thousand. Seven or eight words lands you in the same territory as a strong password.

One more nuance: the word list size matters. A list of 7,776 words (the classic diceware size) gives about 12.9 bits per word instead of 11, so five words from that list reach 65 bits. When comparing passphrase generators, the list size is part of the strength claim — a bigger list means more entropy per word.

The memory question

Here's where passphrases earn their reputation. Human memory is bad at random characters and decent at sequences of meaningful chunks. correct-horse-battery-staple-truck is five chunks your brain can hold; xQ9$mK2!vLz#pR4&wN is sixteen chunks of noise that evaporate the moment you look away.

This matters in exactly one situation: secrets you must type from memory. That's your password manager's master password, your device unlock, maybe your email account — the handful of credentials that guard everything else. For these, a passphrase of 6–8 words is the sweet spot: strong enough by the maths above, and actually memorisable with a day or two of practice.

For everything else — the other two hundred accounts — memorability is irrelevant because you shouldn't be memorising them at all. They live in a password manager, which autofills them. Here the password wins on pure efficiency: 20 random characters is stronger than any passphrase you'd bother typing, it's shorter to store, and you never look at it. When a machine does the remembering, give the machine the densest randomness you can.

A simple rule for picking

• Will a human type this from memory? Use a passphrase of 6–8 randomly chosen words. Master passwords, disk encryption, device PINs (well, those are a separate topic).
• Will a password manager handle it? Use a random password of 16–24 characters from the full character set. Longer is always fine; there's no downside.
• Does the site restrict length or characters? Some older systems cap passwords at 12 or 16 characters or forbid symbols. Generate the longest random password the rules allow — a 12-character random password (79 bits) still beats an 8-character "clever" one by an astronomical margin.
• Is it shared verbally, like a Wi-Fi password for guests? A passphrase wins again — try reading xQ9$mK2!vLz# over the phone versus correct-horse-battery-staple.

The honest caveat

All of the maths above assumes the words or characters were chosen by a genuine random process. This is the part people get wrong most often. A passphrase you invent — your favourite quote, song lyrics, "clever" substitutions — is not a random passphrase; it's a human pattern, and human patterns are exactly what attackers model first. Studies of leaked password databases consistently show that human-chosen "random-looking" secrets cluster into a tiny fraction of the theoretical space.

So the rule is absolute in both directions: generate passwords with a proper generator using your operating system's secure random source, and generate passphrases by rolling dice or using a generator built on the same secure randomness — never by picking words that feel random. The Passphrase Generator and the Password Generator on this site both use your browser's cryptographically secure random number generator, which is the right foundation for either choice.

And one final note that applies to both: no amount of entropy survives reuse, phishing, or storage in plaintext. A 105-bit password used on twelve sites is twelve copies of one secret, and the weakest site's breach becomes all twelve sites' breach. Generate something strong, store it properly, and never reuse it — whichever form you pick.

A quick word on memorisation technique

If you've settled on a passphrase for your master password, don't just stare at it — use it. Type it a dozen times on the first day and you'll find your fingers learn it before your conscious mind does. Some people build a mental image linking the words together (a fabric woven from ideals, wandering across sand), which sounds silly and works surprisingly well. Obviously avoid the sticky note on the monitor — but writing the passphrase on paper kept somewhere genuinely safe while you're learning it is a reasonable temporary measure, and far better than falling back to a weaker secret you can remember immediately. After a week of daily use, you won't need the paper, and you'll have a secret that's both strong and truly yours.

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