iDestin/nanoid

A tiny (130 bytes), secure, URL-friendly, unique string ID generator for JavaScript

Nano ID

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

“An amazing level of senseless perfectionism, which is simply impossible not to respect.”

• Small. 130 bytes (minified and gzipped). No dependencies. Size Limit controls the size.
• Safe. It uses hardware random generator. Can be used in clusters.
• Short IDs. It uses a larger alphabet than UUID (A-Za-z0-9_-). So ID size was reduced from 36 to 21 symbols.
• Portable. Nano ID was ported to 20 programming languages.

import { nanoid } from 'nanoid'
model.id = nanoid() //=> "V1StGXR8_Z5jdHi6B-myT"

Supports modern browsers, IE with Babel, Node.js and React Native.

Table of Contents

• Comparison with UUID
• Benchmark
• Security
• Install
• API
  • Blocking
  • Async
  • Non-Secure
  • Custom Alphabet or Size
  • Custom Random Bytes Generator
• Usage
  • React
  • React Native
  • PouchDB and CouchDB
  • Web Workers
  • Jest
  • CLI
  • Other Programming Languages
• Tools

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 4 times smaller than uuid/v4 package: 130 bytes instead of 423.

Benchmark

$ node ./test/benchmark.js
crypto.randomUUID         21,119,429 ops/sec
uuid v4                   20,368,447 ops/sec
@napi-rs/uuid             11,493,890 ops/sec
uid/secure                 8,409,962 ops/sec
@lukeed/uuid               6,871,405 ops/sec
nanoid                     5,652,148 ops/sec
customAlphabet             3,565,656 ops/sec
secure-random-string         394,201 ops/sec
uid-safe.sync                393,176 ops/sec
shortid                       49,916 ops/sec

Async:
nanoid/async                 135,260 ops/sec
async customAlphabet         136,059 ops/sec
async secure-random-string   135,213 ops/sec
uid-safe                     119,587 ops/sec

Non-secure:
uid                       58,860,241 ops/sec
nanoid/non-secure          2,744,615 ops/sec
rndm                       2,718,063 ops/sec

Test configuration: ThinkPad X1 Carbon Gen 9, Fedora 36, Node.js 18.9.

Security

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

• Unpredictability. Instead of using the unsafe Math.random(), Nano ID uses the crypto module in Node.js and the Web Crypto API in browsers. These modules use unpredictable hardware random generator.

• Uniformity. random % alphabet is a popular mistake to make when coding an ID generator. The distribution 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.

  

• Well-documented: all Nano ID hacks are documented. See comments in the source.

• Vulnerabilities: to report a security vulnerability, please use the Tidelift security contact. Tidelift will coordinate the fix and disclosure.

Install

npm install --save nanoid

Nano ID 4 works only with ESM projects, in tests or Node.js scripts. For CommonJS you need Nano ID 3.x (we still support it):

npm install --save nanoid@3

For quick hacks, you can load Nano ID from CDN. Though, it is not recommended to be used in production because of the lower loading performance.

import { nanoid } from 'https://cdn.jsdelivr.net/npm/nanoid/nanoid.js'

API

Nano ID has 3 APIs: normal (blocking), asynchronous, and non-secure.

By default, Nano ID uses URL-friendly symbols (A-Za-z0-9_-) and returns an ID with 21 characters (to have a collision probability similar to UUID v4).

Blocking

The safe and easiest way to use Nano ID.

In rare cases could block CPU from other work while noise collection for hardware random generator.

import { nanoid } from 'nanoid'
model.id = nanoid() //=> "V1StGXR8_Z5jdHi6B-myT"

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

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

Don’t forget to check the safety of your ID size in our ID collision probability calculator.

You can also use a custom alphabet or a random generator.

Async

To generate hardware random bytes, CPU collects electromagnetic noise. For most cases, entropy will be already collected.

In the synchronous API during the noise collection, the CPU is busy and cannot do anything useful (for instance, process another HTTP request).

Using the asynchronous API of Nano ID, another code can run during the entropy collection.

import { nanoid } from 'nanoid/async'

async function createUser() {
  user.id = await nanoid()
}

Read more about entropy collection in crypto.randomBytes docs.

Unfortunately, you will lose Web Crypto API advantages in a browser if you use the asynchronous API. So, currently, in the browser, you are limited with either security (nanoid), asynchronous behavior (nanoid/async), or non-secure behavior (nanoid/non-secure) that will be explained in the next part of the documentation.

Non-Secure

By default, Nano ID uses hardware random bytes generation for security and low collision probability. If you are not so concerned with security, you can use it for environments without hardware random generators.

import { nanoid } from 'nanoid/non-secure'
const id = nanoid() //=> "Uakgb_J5m9g-0JDMbcJqLJ"

Custom Alphabet or Size

customAlphabet returns a function that allows you to create nanoid with your own alphabet and ID size.

import { customAlphabet } from 'nanoid'
const nanoid = customAlphabet('1234567890abcdef', 10)
model.id = nanoid() //=> "4f90d13a42"

import { customAlphabet } from 'nanoid/async'
const nanoid = customAlphabet('1234567890abcdef', 10)
async function createUser() {
  user.id = await nanoid()
}

import { customAlphabet } from 'nanoid/non-secure'
const nanoid = customAlphabet('1234567890abcdef', 10)
user.id = nanoid()

Check the safety of your custom alphabet and ID size in our ID collision probability calculator. For more alphabets, check out the options in nanoid-dictionary.

Alphabet must contain 256 symbols or less. Otherwise, the security of the internal generator algorithm is not guaranteed.

In addition to setting a default size, you can change the ID size when calling the function:

import { customAlphabet } from 'nanoid'
const nanoid = customAlphabet('1234567890abcdef', 10)
model.id = nanoid(5) //=> "f01a2"

Custom Random Bytes Generator

customRandom allows you to create a nanoid and replace alphabet and the default random bytes generator.

In this example, a seed-based generator is used:

import { customRandom } from 'nanoid'

const rng = seedrandom(seed)
const nanoid = customRandom('abcdef', 10, size => {
  return (new Uint8Array(size)).map(() => 256 * rng())
})

nanoid() //=> "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 customRandom, you can get the default alphabet using the urlAlphabet.

const { customRandom, urlAlphabet } = require('nanoid')
const nanoid = customRandom(urlAlphabet, 10, random)

Asynchronous and non-secure APIs are not available for customRandom.

Note, that between Nano ID versions we may change random generator call sequence. If you are using seed-based generators, we do not guarantee the same result.

Usage

React

There’s no correct way to use Nano ID for React key prop since it should be consistent among renders.

function Todos({todos}) {
  return (
    <ul>
      {todos.map(todo => (
        <li key={nanoid()}> /* DON’T DO IT */
          {todo.text}
        </li>
      ))}
    </ul>
  )
}

You should rather try to reach for stable ID inside your list item.

const todoItems = todos.map((todo) =>
  <li key={todo.id}>
    {todo.text}
  </li>
)

In case you don’t have stable IDs you'd rather use index as key instead of nanoid():

const todoItems = todos.map((text, index) =>
  <li key={index}> /* Still not recommended but preferred over nanoid().
                      Only do this if items have no stable IDs. */
    {text}
  </li>
)

In case you just need random IDs to link elements like labels and input fields together, useId is recommended. That hook was added in React 18.

React Native

React Native does not have built-in random generator. The following polyfill works for plain React Native and Expo starting with 39.x.

1. Check react-native-get-random-values docs and install it.
2. Import it before Nano ID.

import 'react-native-get-random-values'
import { nanoid } from 'nanoid'

PouchDB and CouchDB

In PouchDB and CouchDB, IDs can’t start with an underscore _. A prefix is required to prevent this issue, as Nano ID might use a _ at the start of the ID by default.

Override the default ID with the following option:

db.put({
  _id: 'id' + nanoid(),
  …
})

Web Workers

Web Workers do not have access to a secure random generator.

Security is important in IDs when IDs should be unpredictable. For instance, in "access by URL" link generation. If you do not need unpredictable IDs, but you need to use Web Workers, you can use the non‑secure ID generator.

import { nanoid } from 'nanoid/non-secure'
nanoid() //=> "Uakgb_J5m9g-0JDMbcJqLJ"

Note: non-secure IDs are more prone to collision attacks.

Jest

Jest test runner with jest-environment-jsdom will use browser’s version of Nano ID. You will need polyfill for Web Crypto API.

import { randomFillSync } from 'crypto'

window.crypto = {
  getRandomValues(buffer) {
    return randomFillSync(buffer)
  }
}

CLI

You can get unique ID in terminal by calling npx nanoid. You need only Node.js in the system. You do not need Nano ID to be installed anywhere.

$ npx nanoid
npx: installed 1 in 0.63s
LZfXLFzPPR4NNrgjlWDxn

Size of generated ID can be specified with --size (or -s) option:

$ npx nanoid --size 10
L3til0JS4z

Custom alphabet can be specified with --alphabet (or -a) option (note that in this case --size is required):

$ npx nanoid --alphabet abc --size 15
bccbcabaabaccab

Other Programming Languages

Nano ID was ported to many languages. You can use these ports to have the same ID generator on the client and server side.

• C#
• C++
• Clojure and ClojureScript
• ColdFusion/CFML
• Crystal
• Dart & Flutter
• Deno
• Go
• Elixir
• Haskell
• Haxe
• Janet
• Java
• Nim
• OCaml
• Perl
• PHP
• Python with dictionaries
• Postgres Extension and Native Function
• R (with dictionaries)
• Ruby
• Rust
• Swift
• Unison
• V
• Zig

For other environments, CLI is available to generate IDs from a command line.

Tools

• ID size calculator shows collision probability when adjusting the ID alphabet or size.
• nanoid-dictionary with popular alphabets to use with customAlphabet.
• nanoid-good to be sure that your ID doesn’t contain any obscene words.