What it does
A good password is long and truly random, so nobody can guess it from your name, a word or a pattern. This page makes passwords from the characters you choose, using your browser’s secure random number source, the same one used for encryption.
It also shows the entropy: how many bits of randomness each password has, which tells you how many guesses an attacker would need. The passwords are made on your device and are never sent or saved. To test a password you already have, use the password strength checker; for random IDs rather than passwords, try the UUID generator.
How to use it
- Set the length. 20 characters is filled in.
- Tick the character sets you want.
- Five passwords appear straight away. Press Copy next to one, or Copy all.
- Press Make new ones for a fresh set (changing a setting does too).
What each setting does
- Length: from 8 to 128 characters. Each extra character multiplies the number of possible passwords.
- How many: 1 to 100 passwords at once.
- Use these characters: lower case, upper case, digits and 27 symbols. Untick symbols for sites that refuse them.
- Leave out look-alikes: removes 0, O, o, 1, l and I, so a password is easy to read and type from paper.
- At least one from each ticked set: for sites that demand a digit or a symbol. Passwords that miss a set are thrown away and drawn again, so the result stays fully random.
Worked example
With length 20 and all four sets ticked there are 89 possible characters. Without the “each set” rule that gives 20 × log2(89) = 129.5 bits. Requiring every set leaves out the few passwords that miss one, so the page shows 129.4 bits. Leaving out look-alikes cuts the pool to 83 characters and gives 127.3 bits, still far beyond any guessing attack.
FAQs
How many bits do I need? 80 bits or more is out of reach of guessing attacks today; this page calls 100 bits and above very strong.
Why is there no word-based (passphrase) mode? Not yet: it needs an open word list, which this page does not include so far.
Is the password stored anywhere? No. Close the page and it is gone, so copy it into your password manager first.
Where the numbers come from
- Random numbers from the Web Crypto API (crypto.getRandomValues), with rejection sampling so every character is equally likely. Entropy is the base-2 logarithm of the number of possible passwords. fibub's own working.
Standard scientific values, such as constants, atomic weights and melting points, are facts found in every textbook; we name where ours were checked. If you are an author or publisher and want a value, a credit or a table changed or removed, tell us and we will act quickly.
Read more on the Blog
- Password entropy explained: how many random bits keep you safe(the full guide)
Last updated 2026-11-10.