A tiny (176 bytes), secure, URL-friendly, unique string ID generator for JavaScript.
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Latest commit 3474132 Nov 20, 2017 @ai ai Update dependencies


Nano ID

A tiny, secure, URL-friendly, unique string ID generator for JavaScript.

var nanoid = require('nanoid')
model.id = nanoid() //=> "Uakgb_J5m9g~0JDMbcJqLJ"

Safe. It uses cryptographically strong random APIs and guarantees a proper distribution of symbols.

Small. Only 179 bytes (minified and gzipped). No dependencies. It uses Size Limit to control size.

Compact. It uses a larger alphabet than UUID (A-Za-z0-9_~) and has a similar number of unique IDs in just 21 symbols instead of 36.

The generator supports Node.js and all browsers starting from IE 11.

Sponsored by Evil Martians


See a good article about random generators theory: Secure random values (in Node.js)


Instead of using the unsafe Math.random(), Nano ID uses the crypto module in Node.js and the Web Crypto API in browsers.


random % alphabet is a popular mistake to make when coding an ID generator. The spread will not be even; there will be a lower chance for some symbols to appear compared to others—so it will reduce the number of tries when brute-forcing.

Nano ID uses a better algorithm and is tested for uniformity:

Nano ID uniformity

Comparison with UUID

Nano ID is quite comparable to UUID v4 (random-based). It has a similar number of random bits in the ID (126 in Nano ID and 122 in UUID), so it has a similar collision probability:

For there to be a one in a billion chance of duplication, 103 trillion version 4 IDs must be generated.

There are two main differences between Nano ID and UUID v4:

  1. Nano ID uses a bigger alphabet, so a similar number of random bits are packed in just 21 symbols instead of 36.
  2. Nano ID code is less than half the size of the uuid/v4 package: 179 bytes instead of 435.


$ ./benchmark
nanoid          375,840 ops/sec
nanoid/generate 268,747 ops/sec
uuid/v4         374,767 ops/sec
shortid          41,260 ops/sec



The main module uses URL-friendly symbols (A-Za-z0-9_~) and returns an ID with 21 characters (to have a collision probability similar to UUID v4).

var nanoid = require('nanoid')
model.id = nanoid() //=> "Uakgb_J5m9g~0JDMbcJqLJ"

Symbols -,.() are not encoded in the URL. If used at the end of a link they could be identified as a punctuation symbol.

If you want to reduce ID length (and increase collisions probability), you can pass the length as an argument:

nanoid(10) //=> "IRFa~VaY2b"

Custom Alphabet or Length

If you want to change the ID's alphabet or length you can use the low-level generate module.

var generate = require('nanoid/generate')
model.id = generate('1234567890abcdef', 10) //=> "4f90d13a42"

Alphabet must contain 256 symbols or less. Otherwise, the generator will not be secure.

Custom Random Bytes Generator

You can replace the default safe random generator using the format module. For instance, to use a seed-based generator.

var format = require('nanoid/format')

function random (size) {
  var result = []
  for (var i = 0; i < size; i++) result.push(randomByte())
  return result

format(random, "abcdef", 10) //=> "fbaefaadeb"

random callback must accept the array size and return an array with random numbers.

If you want to use the same URL-friendly symbols with format, you can get the default alphabet from the url module:

var url = require('nanoid/url')
format(random, url, 10) //=> "93ce_Ltuub"

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