What is entropy, and how many bits do I need?

Entropy measures how many guesses an attacker needs, on a log scale — each extra bit doubles the work. Under 28 bits is cracked instantly; around 60 is reasonable for a low-value login; 80 or more is comfortable for anything you care about. A 16-character password drawn from all four character types is about 100 bits.

Is a longer password better than a more complicated one?

Yes, and by a wide margin. Adding one character multiplies the search space by the size of the alphabet; adding symbols to a short password only widens the alphabet a little. Twenty lowercase letters beat eight characters of mixed punctuation, and they are far easier to type on a phone.

Why exclude look-alike characters?

Because capital I, lowercase l and the digit 1 are indistinguishable in many fonts, as are capital O and zero. If a password will be read off a screen, dictated over a phone or printed on a card, dropping those characters costs about half a bit each and prevents a genuinely common support problem.

Password Generator

Build passwords to whatever rules the site in front of you insists on — a length, a symbol, no look-alike characters — and see how strong the result actually is rather than trusting a coloured bar. Every password is drawn in the browser, and the page reports the entropy in bits so you can tell the difference between a password that looks complicated and one that is genuinely hard to guess.

Length16

How many5

Lowercase — a to z

Uppercase — A to Z

Numbers — 0 to 9

Symbols — !@#$%

Avoid look-alike characters

Drops I, l, 1, O, 0 and friends — worth it for a password someone has to read aloud or type from a screen.

Seed

Change this for a completely different set. Read the note under the result before using one of these on a real account.

Result

lKnN0vI.Qq5//yA9
wSBkXv$u4/nn;!Jf
o*:RHlB88oc?k6+;
6,kfSzI&R4$s/1ov
G5{ur=AKw&2Ad[5;

16 characters from a pool of 86 — about 103 bits of entropy. Very strong — good for anything. These are generated from the seed above, so the same seed always gives the same list: treat them as strong-looking examples and change the seed to a number nobody else would guess before using one, or let your password manager generate the one you actually rely on.

Nothing is uploaded — this tool runs inside your browser, so your files never leave your device.

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Why use this tool

6 to 64 characters, up to 30 at a time
Guarantees at least one character from every type you switch on
Optional exclusion of I, l, 1, O and 0 for passwords you have to read aloud
Shows entropy in bits, with a plain-English verdict on what that means

How it works

1Set the length, and switch on the character types the site requires.
2Change the seed until you see a set you like.
3Copy one — then read the note underneath about when to use your password manager instead.

Password Generator — frequently asked questions

Read this one carefully. The passwords here are derived from the seed number, which makes them reproducible — the same seed always produces the same list, and the seed range is small. That is deliberate, because it keeps the tool testable, but it means anybody who guessed your seed could regenerate your password. For an account that matters, let your password manager or your browser generate it: those use a cryptographic random source that nothing can reproduce.

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