🔑 Passphrase Generator (Diceware Style)
By ToolNimba Security Team · Reviewed by ToolNimba Editorial Review, security and privacy content · Updated 2026-06-19
This tool helps you create a strong, memorable passphrase, but it cannot guarantee account security on its own. Use a unique passphrase per account, enable two-factor authentication where available, and store secrets in a reputable password manager. This is general information, not professional security advice.
Set your options and press Generate passphrases. Words are chosen in your browser with the Web Crypto API and nothing is sent anywhere.
A passphrase is a password made from several random words instead of a jumble of symbols, so it is far easier to remember and type while staying hard to guess. This generator picks words from a built-in 256-word list using your browser cryptographic randomness, joins them with the separator you choose, and can capitalize each word or add a digit. It also shows the approximate entropy in bits so you can see how strong the result is. Nothing is sent over the network: every passphrase is built locally and never leaves your device.
What is the Passphrase Generator?
The idea behind a passphrase comes from Diceware, a method created by Arnold Reinhold in 1995. In the original scheme you roll five dice to pick a word from a numbered list, and stringing several such words together gives a password that is both memorable for a human and statistically very hard for a computer to brute-force. This tool follows the same principle but replaces the dice with crypto.getRandomValues, the browser cryptographically secure random number generator, so the choices are unpredictable without you needing any dice.
Strength is measured in bits of entropy. Each word is chosen independently from a list of fixed size, so each word adds log2(listSize) bits. With the 256-word list used here, every word contributes exactly 8 bits, and a passphrase of N words has about N x 8 bits of entropy. Four words give roughly 32 bits, five give 40, and so on. Adding one random digit adds about another 3.3 bits (log2 of 10). Crucially, entropy depends on the number of equally likely choices, not on whether the result looks complicated, so a long string of random words can be much stronger than a short password full of symbols.
The security of a passphrase rests entirely on the words being chosen at random by the tool, not by you. A phrase you invent yourself, like a favourite song lyric or a pet name plus a year, has very little real entropy because attackers feed exactly those patterns into their cracking dictionaries. By contrast a machine-chosen phrase such as river-table-honest-cloud is short to read but draws from an enormous space of possibilities. Use a longer phrase (five or six words) for accounts that matter, and never reuse the same passphrase across different sites.
When to use it
- Creating a master password for a password manager that you must type from memory.
- Generating a strong but memorable login for an account you sign into often on a phone or TV where symbols are awkward.
- Producing a shared device or Wi-Fi password that people can read aloud and type without mistakes.
- Replacing weak, reused passwords with unique passphrases that are easy to recall and hard to crack.
How to use the Passphrase Generator
- Choose how many words you want (four is a sensible minimum, five or six for important accounts).
- Pick a separator: a hyphen, dot, underscore, space, or none.
- Decide whether to capitalize each word and whether to append a random digit.
- Set how many passphrases to generate, then press Generate passphrases.
- Read the approximate entropy in the status line, then copy the passphrase you like.
Formula & method
Worked examples
You generate a 4-word passphrase from the 256-word list, no extra digit.
- Bits per word = log2(256) = 8
- Total entropy = 4 x 8 = 32 bits
- Number of possible phrases = 256^4 = 2^32 ≈ 4.29 billion
Result: A 4-word phrase such as river-table-honest-cloud carries about 32 bits of entropy
You generate a 5-word passphrase and append one random digit.
- Words contribute 5 x log2(256) = 5 x 8 = 40 bits
- One random digit adds log2(10) ≈ 3.32 bits
- Total entropy ≈ 40 + 3.32 = 43.32 bits
Result: A phrase like Maple.Stone.Bridge.Quiet.North7 carries about 43.3 bits of entropy
Approximate entropy and strength by word count (256-word list, no extra digit)
| Words | Entropy (bits) | Possible phrases | Rough strength |
|---|---|---|---|
| 3 | 24 bits | 256^3 ≈ 16.8 million | Weak, demo only |
| 4 | 32 bits | 256^4 ≈ 4.29 billion | Reasonable |
| 5 | 40 bits | 256^5 ≈ 1.1 trillion | Strong |
| 6 | 48 bits | 256^6 ≈ 281 trillion | Strong |
| 8 | 64 bits | 256^8 ≈ 1.8 x 10^19 | Very strong |
Entropy guidance for choosing a passphrase length
| Entropy | What it suits |
|---|---|
| Under 40 bits | Low value or throwaway logins only |
| 40 to 60 bits | Everyday accounts with rate limiting |
| 60 to 80 bits | Important accounts and password manager unlock |
| Over 80 bits | High value secrets and encryption keys |
Common mistakes to avoid
- Choosing the words yourself instead of letting the tool pick. Human-chosen words follow predictable patterns and are exactly what cracking dictionaries target. Entropy only counts if each word is picked at random by the generator, so let the tool do the choosing.
- Using too few words. A 3-word phrase from a small list is well within reach of modern cracking hardware. Use at least four words, and five or six for anything that protects money, email or other accounts.
- Reusing the same passphrase on multiple sites. If one site is breached, attackers will try that passphrase everywhere. Generate a fresh, unique passphrase per account and store them in a password manager.
- Assuming added symbols make it dramatically stronger. Sprinkling in a symbol barely raises entropy compared with adding another whole word. Length and genuine randomness matter far more than how complicated the phrase looks.
Glossary
- Passphrase
- A password made of several words, easier to remember than a random character string while remaining hard to guess.
- Diceware
- A method, devised by Arnold Reinhold, of building passphrases by selecting words at random from a numbered list, traditionally using dice.
- Entropy
- A measure of unpredictability in bits. Each added bit doubles the number of equally likely possibilities an attacker must try.
- Word list
- The fixed set of words the generator draws from. A larger list adds more bits of entropy per word.
- CSPRNG
- A cryptographically secure pseudo-random number generator, such as the browser crypto.getRandomValues, used here to pick words unpredictably.
Frequently asked questions
Are passphrases more secure than passwords?
For the same memorability, yes. A handful of truly random words gives far more entropy than a short password, and it is easier to remember and type. The strength comes from the words being chosen at random and from using enough of them, typically four or more.
How many words should my passphrase have?
Four words is a sensible minimum for everyday use. For important accounts, your email, your bank, or the master password of a password manager, use five or six words. Each extra word from this 256-word list adds 8 bits of entropy.
What is Diceware?
Diceware is a technique created by Arnold Reinhold in 1995 for generating passphrases. You roll dice to select words at random from a numbered list and combine them. This tool follows the same idea but uses the browser secure random generator instead of physical dice.
How is the entropy calculated?
Entropy equals the number of words times log2 of the list size. With a 256-word list, log2(256) is 8, so each word adds 8 bits and a phrase of N words has about N times 8 bits. Appending one random digit adds about 3.3 more bits.
Is this passphrase generator safe to use?
Yes. It runs entirely in your browser using crypto.getRandomValues, makes no network requests, and never transmits or stores what it generates. You can confirm by going offline before generating. As with any tool, only use it for passphrases you keep private.
Can I add my own words or use a bigger list?
This tool uses a fixed built-in list of 256 short, common words for predictable 8-bits-per-word entropy. To get more bits per word you would need a larger list, but you can always raise the strength here simply by choosing more words.
Sources
- Diceware Passphrase Home Page , Arnold G. Reinhold
- Digital Identity Guidelines: Authentication and Lifecycle Management (SP 800-63B) , U.S. National Institute of Standards and Technology