Create strong random passwords or easy to type passphrases, see their strength in bits, and copy them straight into your password manager.
Generated on your device. Passwords are never stored, logged or sent to Ur Next Door.
People are predictable. We pick a word, capitalise the first letter, and add a year or an exclamation mark at the end, and password cracking software tries exactly those patterns first. A password chosen by a secure random generator has no pattern to exploit, so an attacker's only option is to try every possibility. This tool builds passwords that way, and shows you how many possibilities there are.
Every character and every word is picked with crypto.getRandomValues(), the browser's cryptographically secure random number generator, never with Math.random(). Turning a random 32 bit number into a choice among, say, 83 characters is where many generators go slightly wrong: taking the remainder after dividing by 83 makes the first few characters a little more likely, because 232 does not divide evenly by 83. This tool uses rejection sampling instead. Any random number in the uneven tail at the very top of the range is thrown away and a new one is drawn, so every character has exactly the same chance. When several character types are ticked, at least one of each is included, and the positions are then shuffled with the same unbiased method.
Entropy measures how many guesses an attacker would need, written as a power of two. For a random password it is length x log2(pool size), where the pool is the number of different characters allowed. With all four types ticked and look-alikes left out, the pool has 83 characters, worth about 6.38 bits each, so a 16 character password has about 102 bits: 2102 possibilities. For a passphrase the pool is the word list. The list built into this page has 428 short, everyday words, worth about 8.74 bits each, so the default of eight words gives about 70 bits. That is why passphrases here default to eight words: a short list needs more words than the famous Diceware list of 7,776 words, which gives about 12.9 bits per word.
The strength label follows widely used bands: under 28 bits very weak, under 36 weak, under 60 fair, under 128 strong, and 128 or more very strong. The time to guess assumes an attacker who has stolen a database of fast, unsalted hashes and can test 10 billion guesses a second, and shows the average time, which is half of trying them all. A website that limits login attempts is far slower to attack, so treat the figure as a worst case.
A 12 character password from the full 90 character pool has 12 x log2(90), about 78 bits. At 10 billion guesses a second, guessing it takes about 450,000 years on average. Shortening it to 8 digits only gives 8 x log2(10), about 27 bits, which a fast attacker gets through in well under a second.
The page creates passwords on your device. They are not saved, not logged and not sent to Ur Next Door or anyone else, and a new one replaces the old one on screen. Use a different password for every account, and store them in a password manager rather than a notes app.
