A short, practical guide to generating and living with strong passwords: how this tool works, when to pick a passphrase over a password, how much length you actually need, and how to store the results without undoing the effort.
How this password generator works
Every password and passphrase is created on your device. When you click generate, the tool calls window.crypto.getRandomValues(), the browser's cryptographically secure random number generator, and uses rejection sampling so every character or word is equally likely. It never uses Math.random(), which is not safe for secrets.
Nothing you generate is sent anywhere. There is no server call, no analytics, and no storage. The strength meter is powered by zxcvbn-ts, which also runs locally in your browser. You can confirm all of this yourself: open your browser's developer tools, watch the Network tab, and generate as many passwords as you like.
The Download offline version button gives you a single HTML file with the same code, both wordlists, and the strength library all inlined. It is byte-for-byte the same logic that runs here, and it works with no network connection at all. The source is open for review on GitHub.
Password vs passphrase: which is more secure?
A random password is a string of unrelated characters like k7$Rf2!qLmz9. A passphrase is a sequence of random words like correct-anchor-vivid-plum-tunnel. Both can be strong. The difference is where the strength comes from and how you handle it.
Entropy is what matters. A password's entropy is its length times the log base 2 of the character-set size. A passphrase's entropy is the word count times the log base 2 of the wordlist size. Six words from the 7776-word EFF list is 6 × log2(7776) ≈ 77 bits. A 12-character password using all 94 printable characters is 12 × log2(94) ≈ 79 bits. Similar strength, very different to type.
Use a passphrase for anything you have to type or remember: your device login, your disk encryption, your password manager's master password. Use a long random password for everything your password manager fills in for you, where you never type it and readability does not matter.
How long should a password be?
Length beats complexity. Adding one character to a password multiplies the number of possible combinations far more than swapping a letter for a symbol does. A long simple password beats a short complex one every time.
Practical entropy targets:
- 60 bits is the realistic minimum for an account you care about.
- 80 bits or more is recommended for anything important. This is a 14-plus character random password or a 7-word passphrase.
- 128 bits or more for high-value targets: your email, your password manager master password, crypto wallets, and disk encryption.
The current NIST SP 800-63B guidance backs this up. It tells services to allow long passwords, to stop forcing periodic resets, and to drop mandatory composition rules like "must contain a symbol." Length and uniqueness are what protect you.
What is password entropy?
Entropy, measured in bits, is how unpredictable a secret is. Each bit doubles the number of guesses an attacker needs. A secret with 40 bits of entropy takes about a trillion guesses to exhaust. At 80 bits it takes about a trillion trillion. Every extra bit doubles the work.
Worked example: a 4-digit PIN has 10,000 possibilities, which is log2(10000) ≈ 13.3 bits. Trivial to crack. Now take four random words from a 7776-word list. That is 7776 × 7776 × 7776 × 7776 ≈ 3.7 × 10^15 combinations, or about 51 bits. The PIN is shorter to type but astronomically weaker. Entropy, not length in characters, is the real measure.
This tool shows the entropy of whatever it generates, calculated directly from the character set or the wordlist. That number is the honest measure of strength, assuming the attacker knows exactly how the secret was made.
Common password mistakes to avoid
- Reusing passwords. One breach then unlocks every account that shares that password. Credential-stuffing attacks are automated and constant. Every account needs its own unique secret.
- Base word with substitutions.
P@ssw0rd!is not clever. Cracking tools apply those exact substitutions first. A predictable word with predictable swaps has almost no real entropy. - Personal information. Names, birthdays, pet names, and sports teams are all in the wordlists attackers use. Anything guessable from your social media is not random.
- Storing them in the browser with no master password. Browser-saved passwords with no master password can be read by anyone with access to your unlocked device, and sometimes by malware.
How to create a strong password
The strongest password is one you never invent yourself. Human-chosen passwords cluster around predictable patterns; a machine picking uniformly at random does not. Put concretely, here is what to do:
- Generate it randomly with this tool, or use a passphrase of six or more words for anything you have to type from memory.
- Aim for at least 80 bits of entropy. That is roughly a 14-character random password or a 7-word passphrase. Watch the entropy readout above and push it higher for important accounts.
- Make every password unique. One password per account means one breach can never cascade into others.
- Store it in a password manager instead of memorising or reusing it, so length and randomness cost you nothing day to day.
- Turn on two-factor authentication, and add a hardware key for your email, bank, and password manager.
Do those five things and the exact characters no longer matter. Length, randomness, and uniqueness are what stop an attacker, not clever substitutions.
How to store your passwords safely
You cannot remember a unique strong password for every account, and you should not try. Use a password manager. It generates, stores, and fills unique passwords so the only secret you have to remember is one strong master passphrase.
Well-regarded options include Bitwarden (open source, free tier, cloud sync), 1Password (polished, paid), and KeePassXC (fully offline, you control the file). Any of them is a massive upgrade over reuse or a notebook.
Protect the manager itself with a long passphrase and turn on two-factor authentication. For your highest-value accounts, add a hardware security key such as a YubiKey. A physical key cannot be phished or copied remotely.
Are online password generators safe?
Every online password generator you do not control is a trust decision. You are trusting that the server generates the password with secure randomness, that it does not log what it made, that it does not tie the password to your IP address or session, and that its connection is not intercepted. You cannot verify any of that from the outside.
A password that touches someone else's server before it reaches you is already a weaker password, because you can no longer be sure you are the only one who has seen it. Local generation removes the entire question. The secret is created on your device, it stays on your device, and the download button lets you cut the network out completely.
This is the same principle behind Blackout VPN: the less anyone else has to be trusted, the safer you are.
Frequently asked questions
Is this password generator really offline?
Yes. Every password and passphrase is generated in your browser using the Web Crypto API. Nothing you generate is sent to a server. You can verify this in DevTools under the Network tab, or download the offline version and run it with no internet connection at all.
What's the difference between the EFF Large and Short wordlists?
The EFF Large wordlist has 7776 words and gives about 12.9 bits of entropy per word. The Short wordlist has 1296 words, gives about 10.3 bits per word, and uses shorter, more memorable words that are easier to type. Large is stronger per word; Short is easier to remember.
How many words should my passphrase have?
Six words from the EFF Large wordlist gives about 77 bits of entropy, which is strong for almost anything. Use seven or eight words for high-value accounts like your email, password manager, or financial logins.
Can I trust the randomness?
This tool uses window.crypto.getRandomValues(), the browser's cryptographically secure random number generator. It never uses Math.random(). Word and character selection uses rejection sampling so every option is equally likely, with no modulo bias.
Do you log or store generated passwords?
No. Nothing is logged, stored, or transmitted. There is no analytics, no cookies, and no persistence. When you close the tab, the generated values are gone.
Can I use this on my phone?
Yes. The tool works in any modern mobile browser. The copy button works on touch devices, and the downloadable offline version can be saved and opened from your phone's files with no connection.