Why entropy per word beats entropy per character for humans
Entropy is entropy — a password's resistance to guessing depends on the total size of the space an attacker has to search, not on whether that space is built from characters or words. The insight behind the passphrase approach, popularized by the XKCD 936 comic, is that humans are far better at memorizing and typing a handful of ordinary words than an equivalent-strength string of random characters and symbols. Four random words can carry roughly the same entropy as eight or nine random characters, but one of those is something you can actually hold in memory and type without hunting for a symbol on your keyboard.
This tool builds exactly that: it picks words from a curated wordlist using crypto.getRandomValues — the same cryptographically secure random source your browser uses for TLS — with rejection sampling to avoid modulo bias, so each word position is drawn uniformly at random from the full list, with no word more likely to appear than any other.
How entropy scales with word count
The entropy calculation for a passphrase mirrors the one for a random-character password, just with words as the unit instead of characters: entropy = log2(wordlist size) × number of words. With a 200-word list, log2(200) is approximately 7.64 bits per word. A 5-word passphrase from that list gives roughly 7.64 × 5 = 38 bits of entropy — the exact figure the tool's own documentation cites, and a useful anchor point for reasoning about longer or shorter phrases.
Entropy by word count (200-word list)
| Words | Entropy (bits, approx) | Roughly comparable to |
|---|---|---|
| 4 | ~31 | A 6-character fully random password |
| 5 | ~38 | An 8-character fully random password |
| 6 | ~46 | A 10-character fully random password |
| 8 | ~61 | A 12–13-character fully random password |
| 10 | ~76 | A 16-character fully random password |
Generating a passphrase
Pick how many words to use, from 4 to 10.
Choose a separator — hyphen, dot, space, or underscore — and whether to capitalize each word.
Click Generate new to roll a fresh passphrase.
Copy it into your password manager, or use it as a master password you'll type from memory.
Choosing a word count for the actual risk level
Word count matters more here than any other setting, exactly as length does for a random-character password — each additional word multiplies the total number of possible passphrases by the wordlist size, compounding fast.
Why capitalization and separators barely move the needle
Toggling capitalization or switching separators changes the passphrase's appearance but adds essentially no entropy, because these choices are typically applied consistently (every word capitalized, one separator throughout) rather than randomized per instance — an attacker who knows the tool's settings already knows the capitalization pattern and separator character, so those choices contribute little to unpredictability. Their real value is readability and compatibility: capitalization can make word boundaries easier to spot at a glance, and switching the separator matters practically when a specific site's password field rejects spaces or a particular symbol.
Why the wordlist itself matters
A curated list of common English words is chosen deliberately for memorability — you're far more likely to correctly recall and retype 'harbor' than an arbitrary rare or obscure word, and a list of familiar words also reduces typos. This isn't a security compromise: entropy depends on the size of the list and the randomness of selection, not on how obscure the individual words are. A 200-word list of common, easy words provides the same log2(200) ≈ 7.64 bits per word as a 200-word list of obscure ones — the underlying approach of picking N words uniformly at random from a fixed-size list is what matters, and this version doesn't support a custom wordlist, though the same principle would apply to one.
Common mistakes
Choosing only 4 words for something high-value, like a password manager's master password, when the extra memorability cost of 2–3 more words is small relative to the entropy gained.
Assuming capitalization or a fancier separator meaningfully strengthens the passphrase — the word count is doing essentially all the real work.
Reusing the same generated passphrase across multiple important accounts — entropy protects against guessing a single passphrase, not against one compromised service exposing it elsewhere.
Sticking with spaces as a separator on a site that silently truncates or rejects them — switch to a hyphen or underscore if a login unexpectedly fails.
Real use cases
Generating a master password for a password manager that you need to type from memory regularly.
Creating a strong Wi-Fi network password that's realistically typeable by guests without a password manager.
Setting a full-disk encryption passphrase that needs to be both strong and rememberable without being written down.
Choosing a passphrase for an account you log into on devices without password-manager autofill, like a shared kiosk or a smart TV.
Frequently asked questions
Q: Why use a passphrase instead of a random password?
A: A 5-word passphrase from a 200-word list has roughly 38 bits of entropy, yet is far easier to remember and type than 8 random characters. The classic XKCD 936 comic explains the underlying idea.
Q: How random is the word selection?
A: Each word is picked with crypto.getRandomValues using rejection sampling to avoid modulo bias — the same CSPRNG that powers TLS in your browser.
Q: Can I add my own wordlist?
A: Not in this version. The built-in list of common English words is curated to be memorable. For a custom list, the underlying approach is identical: pick N words uniformly at random.
Q: How many words do I need?
A: For most logins, 5–6 words from a 200-word list is comparable to a 12-character random password. Use more if the passphrase protects something especially valuable.
Q: Are spaces safe to use?
A: Yes — most sites accept spaces in passwords. If a particular site disallows them, switch the separator to a hyphen or underscore instead.
Q: If I add a random extra character to my passphrase myself, does that help more than adding a word?
A: Not proportionally — an extra character from a small guessable set adds far less entropy than an extra word drawn from the full wordlist, since one more word multiplies the search space by the wordlist size rather than by a handful of character options.
Generate a passphrase now
Create yours with the Passphrase Generator. Need a fully random character-based password instead? Try the Password Generator. Want to check an existing password's strength? Use the Password Strength Checker, or encrypt sensitive text directly with Encrypt & Decrypt Text.
