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Easily generate random strings like passwords, with simple options for specifying a length and for using patterns of numeric, alpha-numeric, alphabetical, special or custom characters. (the original "generate-password")
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randomatic NPM version NPM monthly downloads NPM total downloads Linux Build Status

Generate randomized strings of a specified length using simple character sequences. The original generate-password.

Please consider following this project's author, Jon Schlinkert, and consider starring the project to show your ❤️ and support.


Install with npm:

$ npm install --save randomatic


var randomize = require('randomatic');


randomize(pattern, length, options);
  • pattern {String}: (required) The pattern to use for randomizing
  • length {Number}: (optional) The length of the string to generate
  • options {Object}: (optional) See available options
  • randomize.isCrypto will be true when a cryptographically secure function is being used to generate random numbers. The value will be false when the function in use is Math.random.


The pattern to use for randomizing

Patterns can contain any combination of the below characters, specified in any order.


To generate a 10-character randomized string using all available characters:

randomize('*', 10);
//=> 'x2_^-5_T[$'

randomize('Aa0!', 10);
//=> 'LV3u~BSGhw'
  • a: Lowercase alpha characters (abcdefghijklmnopqrstuvwxyz')
  • A: Uppercase alpha characters (ABCDEFGHIJKLMNOPQRSTUVWXYZ')
  • 0: Numeric characters (0123456789')
  • !: Special characters (~!@#$%^&()_+-={}[];\',.)
  • *: All characters (all of the above combined)
  • ?: Custom characters (pass a string of custom characters to the options)


The length of the string to generate


  • randomize('A', 5) will generate a 5-character, uppercase, alphabetical, randomized string, e.g. KDJWJ.
  • randomize('0', 2) will generate a 2-digit random number
  • randomize('0', 3) will generate a 3-digit random number
  • randomize('0', 12) will generate a 12-digit random number
  • randomize('A0', 16) will generate a 16-character, alpha-numeric randomized string

If length is left undefined, the length of the pattern in the first parameter will be used. For example:

  • randomize('00') will generate a 2-digit random number
  • randomize('000') will generate a 3-digit random number
  • randomize('0000') will generate a 4-digit random number...
  • randomize('AAAAA') will generate a 5-character, uppercase alphabetical random string...

These are just examples, see the tests for more use cases and examples.


These are options that can be passed as the third argument.


Type: String

Default: undefined

Define a custom string to be randomized.


  • randomize('?', 20, {chars: 'jonschlinkert'}) will generate a 20-character randomized string from the letters contained in jonschlinkert.
  • randomize('?', {chars: 'jonschlinkert'}) will generate a 13-character randomized string from the letters contained in jonschlinkert.


Type: String|Array

Default: undefined

Specify a string or array of characters can are excluded from the possible characters used to generate the randomized string.


  • randomize('*', 20, { exclude: '0oOiIlL1' }) will generate a 20-character randomized string using all of possible characters except for 0oOiIlL1.

Usage Examples

  • randomize('A', 4) (whitespace insenstive) would result in randomized 4-digit uppercase letters, like, ZAKH, UJSL... etc.
  • randomize('AAAA') is equivelant to randomize('A', 4)
  • randomize('AAA0') and randomize('AA00') and randomize('A0A0') are equivelant to randomize('A0', 4)
  • randomize('aa'): results in double-digit, randomized, lower-case letters (abcdefghijklmnopqrstuvwxyz)
  • randomize('AAA'): results in triple-digit, randomized, upper-case letters (ABCDEFGHIJKLMNOPQRSTUVWXYZ)
  • randomize('0', 6): results in six-digit, randomized numbers (0123456789)
  • randomize('!', 5): results in single-digit randomized, valid non-letter characters (`~!@#$%^&()_+-={}[]
  • randomize('A!a0', 9): results in nine-digit, randomized characters (any of the above)

The order in which the characters are defined is insignificant.



Pull requests and stars are always welcome. For bugs and feature requests, please create an issue.

Running Tests

Running and reviewing unit tests is a great way to get familiarized with a library and its API. You can install dependencies and run tests with the following command:

$ npm install && npm test
Building docs

(This project's is generated by verb, please don't edit the readme directly. Any changes to the readme must be made in the readme template.)

To generate the readme, run the following command:

$ npm install -g verbose/verb#dev verb-generate-readme && verb

Related projects

You might also be interested in these projects:

  • pad-left: Left pad a string with zeros or a specified string. Fastest implementation. | homepage
  • pad-right: Right pad a string with zeros or a specified string. Fastest implementation. | homepage
  • repeat-string: Repeat the given string n times. Fastest implementation for repeating a string. | homepage


Commits Contributor
56 jonschlinkert
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4 kivlor
2 realityking
2 ywpark1
1 TrySound
1 drag0s
1 paulmillr
1 sunknudsen
1 faizulhaque-tp
1 michaelrhodes


Jon Schlinkert


Copyright © 2018, Jon Schlinkert. Released under the MIT License.

This file was generated by verb-generate-readme, v0.8.0, on October 23, 2018.

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