The xkcd comic settled this for a lot of people: four common words beat an unpronounceable scramble, and you can actually remember it. The comic is right, and the reason it is right gets misremembered in a way that produces genuinely weak passphrases.
The thing that makes a passphrase strong
It is not that it is long. It is that the words were chosen randomly, from a large list.
Strength comes from how many equally likely possibilities an attacker has to work through. Pick four words at random from a 7,776-word list — the standard Diceware list — and there are 7,776⁴ combinations, about 3.6 × 10¹⁵. That is roughly 52 bits of entropy, and it does not matter at all that an attacker knows you used exactly this method with exactly this list. Knowing the method does not narrow the search.
Now pick four words yourself. You will not pick randomly, because people cannot. You will pick words that relate to each other, words you like, words from your life. correct horse battery staple is famously four random words — and because it is now the most famous passphrase in the world, it is in every cracking dictionary and falls immediately.
The gap between those two cases is enormous. The same four-word structure gives you 52 bits when a machine picks and maybe 20 when you do.
Where each one wins
| Random passphrase | Random password | |
|---|---|---|
| Typing on a phone or TV remote | Much easier | Painful |
| Saying out loud | Possible | No |
| Remembering it | Realistic | No |
| Entropy per keystroke | Low | High |
| Fits a 16-character limit | Rarely | Yes |
| Survives "must contain a symbol" | Awkwardly | Yes |
That entropy-per-keystroke row is the real trade. A 20-character random password carries about 128 bits. A four-word passphrase of similar typed length carries about 52. The password is denser — but you will never memorise it, and that is fine when it lives in a password manager.
So: which, for what
Use a passphrase for the handful you must type from memory. Your password manager's master password. Your device login. Your disk encryption key. These get typed on keyboards, phones, occasionally a games console, and they are the ones where memorability is a hard requirement rather than a convenience. Use six words rather than four for these — around 77 bits, and still easy.
Use a random password for everything else. Every site account goes in a password manager, gets 20-plus random characters, and you never see it again. There is no memorability requirement, so take the denser option. The generator here does this and shows you the resulting crack time against several attackers, which makes the length trade-off concrete rather than theoretical.
Generating a passphrase properly
The classic method is physical: roll five dice, read the five-digit number off a Diceware word list, repeat. It is slow and it is genuinely unbeatable for randomness, because the dice do not have opinions.
The practical method is a generator that uses a cryptographically secure random source against a real word list. What matters in either case is that you do not get to veto words. The moment you re-roll because a combination "doesn't feel right", you have reintroduced human choice and thrown away the property that made it strong.
Two smaller points. Separators barely matter — spaces, hyphens or nothing add almost nothing, so pick whatever the site accepts. And capitalising the first letter adds about one bit, which is to say nothing; do it if a form demands it, not for security.
The length limit problem
A six-word passphrase runs 30 to 40 characters, and a surprising number of sites silently cap input at 16 or 20 — sometimes truncating without telling you, which is how you end up locked out. If you hit that, the site has told you something about how it treats security, and a random password is the pragmatic answer for that account.
If you want to check a phrase's length before pasting it into a form that will quietly cut it, the character counter is a faster way to find out than discovering it at the login screen.
What neither one fixes
Same caveat as always, because it is the one that actually costs people their accounts. Neither a passphrase nor a password helps if you reuse it and one of those sites gets breached, and neither helps if you type it into a convincing fake login page. Unique credentials per site and two-factor authentication do more than any choice on this page.
Pick whichever you will actually use consistently. A six-word passphrase you type correctly every day beats a 30-character password you find so annoying that you turn it into Password1 three weeks later.
For the accounts that live in a password manager, the password generator is the right tool — set it to 20 characters and watch what the crack time does as you drag the slider. It uses your browser's cryptographic random source rather than Math.random(), which matters more than it sounds, and nothing leaves the page.
If the table above left you wondering what those crack times actually mean — why the same password can be unbreakable against one attacker and gone in a day against another — how long it takes to crack a password works through all five scenarios and where the guess rates come from.
Frequently asked questions
Is a passphrase safer than a password?
A randomly generated passphrase is much safer than a short password and much easier to remember. A passphrase where you chose the words yourself is usually far weaker than it looks, because human word choice is highly predictable.
How many words should a passphrase have?
Four randomly chosen words from a large list gives about 52 bits, which is reasonable. Six gives about 77 bits and is the right target for anything important — your password manager master password, device login or disk encryption.
Is "correct horse battery staple" a good passphrase?
It was a good illustration and is now a terrible passphrase. Being the most famous example in the world put it in every cracking dictionary, so it falls instantly. The method is sound; that specific output is burned.
Do I need separators or capital letters in a passphrase?
Not for security. Separators add almost nothing and a leading capital adds about one bit. Use whatever the site’s rules force you into, and get your strength from the number of randomly chosen words instead.
What if a site limits password length?
A six-word passphrase runs 30 to 40 characters and some sites cap input at 16 or 20, occasionally truncating silently. If you hit that limit, use a random password for that account — and note what the cap tells you about the site.
Last updated September 19, 2026