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Complexify helps you to accurately gauge the quality of a user's password to give them visual feedback, and to enforce a minimum level of security.

branch: master


Websites have a responsibility to users to accurately tell them how good a password is, and this is not an easy job.

  • If your password is 8 characters long and only formed of lower case characters, you need to make it better, perhaps by adding a number or more characters.
  • If your password is 25 characters long but happens to not contain a number, you shouldn't be forced by a password security policy to add one, you clearly have a very secure password.

Complexify aims to provide a good measure of password complexity for websites to use both for giving hints to users in the form of strength bars, and for casually enforcing a minimum complexity for security reasons.

Note: I use the term 'casually' because this is only client-side validation and anyone could turn it off. I recommend implementing a minimum length check server-side as well. In the future I may code up this algorithm for use server-side.

Complexity Rating

Complexify's default settings will enforce a minimum level of complexity that would mean brute-forcing should take ~600 years on a commodity desktop machine. The 'perfect' password used to scale the complexity percentage would take 3x10^33 years. These are equivalent to a 12 character password with uppercase, lowercase and numbers included, and a 25 character password with uppercase, lowercase, numbers and a wide range of punctuation.


Complexify supports Unicode and will add appropriate complexity for the size of character set included in a password.

For example, as there are 96 Hiragana characters defined in the Unicode specification, including one of these will increase the brute-force complexity by 96.

The rationale behind this is that in an attacker were wanting to include Japanese passwords in his attack, he/she may choose to include the Hiragana set in his/her attack, but not the Katakana set. Complexify divides Unicode into 94 appropriately grouped sets.

Using a Password Ban List

If you wish to provide a list of passwords that will always return 0% complexity, this is now possibly by passing a bannedPasswords array into the options of Complexify, or by setting the global COMPLEXIFY_BANLIST variable to an array of passwords. Including jquery.complexify.banlist.js in your page is a quick and easy way to do the latter option.

The ban list has 2 modes: 'loose' and 'strict', with 'strict' being the default.

  • strict: If a password is contained in the banned list, or contained in any item of the banned list, the password will fail. This means that "123456" will fail as it is in the banned list, but "123" and "345" will also fail as they are substrings of a password in the list.
  • loose: If a password exactly matches one in the banned list, the password will fail.

By default, the banned passwords list is empty and therefore this has no effect.

Version History

0.3 - Banned password list support, better event binding.

0.2 - Unicode support
Note: most passwords using punctuation will score slightly lower as the punctuation set has been split into multiple sets.

0.1 - Basic implementation

Alternative Implementations

Several people have kindly open-sourced their implementations of this algorithm in other languages:

For more information, visit the website.

This code is distributed under the WTFPL v2 licence.

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