How it works
The strength of a randomly generated password does not depend on it "looking complicated" but on how many possible combinations the generator had to choose from. That number is expressed in bits of entropy: each bit doubles an attacker's work. A 20-character password that mixes lowercase, uppercase, digits and symbols comes from a 94-character alphabet and has about 131 bits; with 8 characters from the same alphabet it drops to 52 bits, which a GPU farm can exhaust in days.
Passphrases trade characters for words. This tool uses the EFF long list, with 7,776 words (6⁵, the combinations of five dice), so each word adds 12.9 bits. Five words give 64.6 bits, the same as 10 fully random characters, but they are far easier to remember and type, which matters for a password manager's master password or disk encryption.
Everything is generated in your browser with crypto.getRandomValues, the operating system's cryptographic generator, and rejection sampling ensures no character comes up more often than another. Neither the generated passwords nor the one you check in the last card leave your device, and the checker is not stored in the share link either.
Examples
20 · a-z A-Z 0-9 !@#…≈ 131 bits20 × log₂(94). Even at 10 billion guesses per second, going through half of the combinations would take about 4.6 × 10²¹ years.5 × EFF≈ 64,6 bits5 × log₂(7776). Against a fast hash, a GPU would take about 45 years on average; if the site stores passwords with bcrypt, more than 45 million.8 · a-z A-Z 0-9 !@#…≈ 52 bitsEight characters are no longer enough if a fast hash leaks: at 10 billion guesses per second, half of the space is covered in about 85 hours.PIN · 61 000 000 · ≈ 19,9 bitsA PIN is only secure because the device or the bank limits attempts. At 100 attempts per hour, trying half of the combinations would take about 208 days; without a limit, an instant.Use cases
- Create unique passwords for each account and store them in a password manager.
- Choose a passphrase for what you have to type from memory: the manager's master password, disk encryption or your computer login.
- Generate service credentials, API keys or database passwords for configuration files and secret managers.
- Create initial passwords in bulk for new users, excluding ambiguous characters so they can be dictated or read from paper without mistakes.
- Adapt to systems with odd rules by removing the symbols they do not accept, such as quotes or backslashes.
- Check whether a password you already use is predictable before deciding whether to change it.
Frequently asked questions
How many bits does a password need?
For a web account protected by rate limiting, 60 bits is more than enough. If the secret could be attacked offline, for example a password manager's master password or a key protecting an encrypted file, aim for 80 or more. Beyond 128 bits there is no practical gain: it is already out of reach for any conceivable attacker.
Is a long password or one with symbols more secure?
The long one. Going from 62 to 94 possible characters, that is, adding symbols, adds 0.6 bits per character; adding one more character adds over 6 bits. That is why NIST, in its SP 800-63B guideline, asks sites to accept long passwords and to stop imposing composition rules such as "at least one symbol".
Why does the passphrase use English words?
Because the EFF list is curated for passphrases: common words, no offensive terms, easy to type and with no word being a prefix of another, which avoids ambiguity when they are joined without a separator. Security does not depend on the language but on the size of the list and on the choice being random; the attacker can know the whole list and still has to try 7,776 options per word.
Why does the checker rate differently from the entropy?
Because they measure different things. Entropy applies to randomly generated secrets, where the exact process is known. A password made up by a person is almost never random: "Argentina2024!" has 14 characters of four kinds, but it is a dictionary word, a year and a symbol at the end, exactly what cracking programs try first. The checker looks for those patterns and estimates how many guesses it would really take.
Is it safe to generate passwords on a web page?
It is if the computation happens in your browser and nothing is sent, which is the case here: you can check it by opening the developer tools and seeing that the network tab records no outgoing data; the only download is the word list, the first time you ask for a passphrase. Even so, for the most critical credentials it is ideal to let the same manager where you will store them generate them, so the password never goes through the clipboard.
Why exclude ambiguous characters?
Because in many typefaces 0 and O, or 1, l and I, are almost identical, and a password someone has to read from paper or dictate over the phone ends up copied wrong. Removing them shrinks the alphabet and the entropy per character slightly, which you can make up for by adding one or two characters of length.