How to use
- Choose Password for random characters or Passphrase for random words.
- Set the length (8 to 128) and tick the character types you want. The default, 20 characters from all four types, is very strong.
- Press Generate new for a fresh one, then Copy.
The password is made in your browser. It is never sent anywhere, saved in your history or added to the page link.
How the strength is calculated
Every character is picked at random from the pool you chose, with no bias (rejected draws are redrawn rather than wrapped around). So the number of possible passwords is easy to count:
entropy (bits) = length × log2(pool size)
passphrase = words × log2(7,776)
The pool is 94 with lowercase, uppercase, numbers and all 32 symbols. Each EFF word adds about 12.9 bits.
Strength labels compare the bits with published reference points: 128 bits is the strength of a 128-bit key, and 112 bits is the lowest key strength NIST SP 800-57 still accepts. 77.5 bits is EFF’s recommended six-word passphrase.
Examples
| Length | All 94 characters | Letters and numbers (62) | Lowercase only (26) |
|---|---|---|---|
| 8 | 52.4 bits | 47.6 bits | 37.6 bits |
| 12 | 78.7 bits | 71.5 bits | 56.4 bits |
| 16 | 104.9 bits | 95.3 bits | 75.2 bits |
| 20 | 131.1 bits | 119.1 bits | 94.0 bits |
| 32 | 209.7 bits | 190.5 bits | 150.4 bits |
Passphrases: 5 words = 64.6 bits, 6 words = 77.5 bits, 7 words = 90.5 bits. Length matters more than symbols: 20 letters and numbers beat 16 characters from all 94.
The fine print on "at least one of each" and look-alikes
“At least one of each type” throws away any password that misses a type and draws a whole new one. That keeps every allowed password equally likely, and the bits shown are counted exactly, so they drop slightly (20 characters: 131.1 → 130.9 bits).
Excluding look-alikes removes 0, O, 1, l and I, shrinking the pool from 94 to 89. Add a character to make up for it.
Passphrase words come from the EFF Large Wordlist (7,776 words, CC BY). Capitalising words adds no strength; adding a number adds about 6 bits for six words.
Need a random number rather than a password, such as a PIN or a raffle draw? Use the random number generator.