Secure password generator

Choose a length and which characters to allow — or switch to passphrase mode and choose how many words — and this generator returns three fresh candidates to pick from, each with its entropy in bits and the time an attacker would expect to need. Free, no account, no e-mail, and nothing generated is stored.

What it does, and why it is here

Two problems, and only one of them is arithmetic. The first is that a password a person invents is not random: it carries patterns, and the software that guesses passwords knows every one of them, including the substitutions that feel clever. This page draws instead from a cryptographically secure random source — not the clock, not anything reproducible — so there is nothing about it to know.

The second is that “strong” is a word with no scale attached. Most generators hand over a string and leave you to guess whether it is good for a decade or falls in an afternoon. This one answers that in the same breath: how many bits went into it, and how long three different kinds of attacker would need.

And it draws three at a time, because choosing is easier than judging. You take whichever reads best; the other two go nowhere.

What you fill in

Two modes, shown side by side, so you can see what the other one offers before switching to it.

Characters — for the passwords a manager fills in

• Length — 8 to 128, offered as steps that mean something rather than one at a time: the floor you can still type by hand, the size a password manager holds, then the lengths long-lived keys are cut to. The default is 24.
• Lowercase, uppercase, digits — on by default. That is the alphabet accepted everywhere.
• Symbols — off by default, and the option worth understanding. They add about half a bit per character, and they are also what login forms most often refuse, truncate or quietly mangle. If a password stops working right after you set it, that is usually why. Four more characters buy more than symbols do, with none of the risk.
• Leave out lookalike characters — drops 0/O and 1/l/I. Worth it whenever the password will be read off one screen and typed into another, or dictated to someone: it costs a little entropy and saves a lot of retyping.

Passphrase — for the two or three you have to remember

• Words — 4 to 8, drawn from the EFF long wordlist: 7,776 common words, 12.9 bits each. Six words match a twelve-character password for strength and are far easier to type on a phone, a console or a TV remote.
• Between the words — a space, a hyphen, a dot, or nothing, because some forms still refuse spaces.
• Capitalise each word and add a digit at the end — both off, and both accounted for under the answer at exactly what they are worth: the digit adds 3.3 bits, one chance in ten; the capitals add nothing at all, since every word gets one and there is nothing left to guess.

The chips above the form are the policies people are actually asked for: twelve characters with a symbol, an eight-digit code, a 63-character Wi-Fi key, a six-word passphrase. A chip carries the policy and never a result — the link is safe to copy and send, because it says what to generate, not what was generated.

What you get back

• Three candidates, each with a copy button. Take one; the other two are not stored, not logged, and not recoverable.
• Length or word count, entropy in bits, and a strength badge — the same for all three, since they came from one policy. Entropy is the honest measure: each extra bit doubles the work of guessing.
• Time to crack, as three attackers rather than one number, because the number depends entirely on how the site you are signing up to stores your password: an online login form throttled to about 100 guesses a second; an offline attack on a slow hash such as bcrypt, about 10,000 a second; a GPU on a fast hash, about 100 billion a second. It is computed from the bits and never from the string — nothing here reads the password it just handed you.
• For a passphrase, where the bits came from, spelled out word by word.

What it does not do

It stores, logs, indexes and counts nothing you generate. There is no account, so there is nothing to attach a password to and no history to leak later; reload the page and the previous three are gone for everyone, ourselves included.

The honest trade-off, since a generator unwilling to state it should not be trusted: the password is drawn on the server and crosses the network once, inside the encrypted connection. For the overwhelming majority of accounts that is a non-issue. For the two or three secrets where you would rather nothing ever left your own machine — a disk encryption key, the master passphrase of your vault — use a generator that runs offline. That is the right answer, and it is not this page.

It also cannot tell you whether a password you already have is any good. It makes new ones; it does not grade old ones. Typing an existing password into any website is a bad habit whatever the site promises.

How long should a password be?

Length is what protects a random password: there is no pattern to shortcut, so an attacker has nothing better than trying everything, and each character multiplies how much everything is. Here is what each length is worth with letters and digits — the alphabet this generator uses by default.

Length	Entropy	Strength	What it suits
12	71 bits	Medium	The practical floor, for a password you must type by hand
16	95 bits	Strong	An account you sign into often
20	119 bits	Strong	Anything holding money or personal data
24	143 bits	Very strong	The default — anything a password manager fills in for you
32	190 bits	Very strong	Long-lived secrets: API keys, service accounts, backups

Symbols raise those figures — sixteen characters go from 95 to 103 bits, twenty-four from 143 to 155 — but notice that four more characters would have bought more than symbols do. For a password standing on its own, with no second factor behind it, current NIST guidance puts the floor at fifteen characters.

Questions

Is it free?

Yes, with no account and no limit. Generate as many as you need.

Do you store the passwords it generates?

No. Your settings come in, three passwords go out, and neither is written to a database, a log or an index. They are not attached to any identity, because the page does not know one.

Can I get the same password twice?

Not deliberately, and not by accident either — at these lengths the number of possibilities is far beyond anything that repeats. Nothing is remembered between requests, so reloading gives you three fresh ones. Copy the one you want before you leave the page.

Which mode should I choose?

Passphrase for the handful you type from memory — the one that unlocks your password manager, the one that unlocks your laptop. Characters for everything else, where a manager does the typing and a shorter random string reaches the same strength.

Is a long password enough on its own?

It defeats one attack out of the three that matter. Length and randomness are exactly what beat offline cracking, where a stolen database is attacked at billions of guesses a second. They do nothing against reuse, where a password leaked by one site is tried automatically against hundreds of others — only a different password per account helps there, which is what generating a new one each time is for. And they do nothing against phishing, where you hand the password over yourself. A password manager and a second factor cover those two.

My employer requires a symbol and a capital. What do I do?

Tick symbols and generate. Composition rules of that kind are discouraged by current guidance, but arguing with a login form has never worked, and a random twenty-character password satisfies every such rule by accident while being stronger than anything the rule was trying to produce.

Is 12 characters still enough?

For an account behind a second factor, yes. For one standing alone, prefer 16 or more — and see the table above for what each length is actually worth.

How often should I change them?

Only when there is a reason: a breach at the site, a password you shared, a login you do not recognise. Scheduled changes were dropped from security guidance years ago; current NIST guidance tells sites not to force them at all.

Where should I keep them?

In a password manager, itself locked with a long passphrase and a second factor. Written on paper in a drawer at home is a distant second — unfashionable, but it defeats every remote attacker, which is most of them.

Sources and further reading

• NIST SP 800-63B, Digital Identity Guidelines — minimum lengths, and the instruction to stop requiring composition rules and periodic changes.
• EFF long wordlist — the 7,776 words the passphrase mode draws from.
• Have I Been Pwned — free check of whether an address or a password has appeared in a known breach.