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. 117 bytes (minified and brotlied). No dependencies.

• Fast. Faster than native crypto.randomUUID().
• Safe. It uses hardware random generator. Can be used in clusters.
• Short IDs. It uses a larger alphabet than UUID (A-Za-z0-9_-).

• Portable. Nano ID was ported

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

[Size Limit]: https://github.com/ai/size-limit

Table of Contents

• Table of Contents
• Comparison with UUID
• Benchmark
• Security
• Install

• API

• Usage

• 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

1. Nano ID is faster than crypto.randomUUID and uuid/v4.

Benchmark

$ node ./test/benchmark.js
nope-id                 59,034,753 ops/sec
nanoid                  38,883,215 ops/sec
customAlphabet          25,481,101 ops/sec
crypto.randomUUID        6,871,047 ops/sec
uuid v4                  6,169,740 ops/sec
@napi-rs/uuid            8,791,173 ops/sec
uid/secure               8,229,214 ops/sec
@lukeed/uuid             6,687,021 ops/sec
nanoid for browser         653,420 ops/sec
secure-random-string       531,531 ops/sec
uid-safe.sync              534,386 ops/sec
Non-secure:
uid                     36,726,989 ops/sec
nanoid/non-secure        2,753,530 ops/sec
rndm                     2,820,063 ops/sec

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

• Uniformity. random % alphabet is a popular mistake to make when coding

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

• Vulnerabilities: to report a security vulnerability, please use

[Secure random values (in Node.js)]: https://gist.github.com/joepie91/7105003c3b26e65efcea63f3db82dfba [better algorithm]: https://github.com/ai/nanoid/blob/main/index.js [the source]: https://github.com/ai/nanoid/blob/main/index.js

Install

npm install nanoid

CDN

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

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).

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.

[ID collision probability]: https://zelark.github.io/nano-id-cc/

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/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 from 1 to 256 symbols. Otherwise, the security of the internal generator algorithm is not guaranteed, and a generator built from an empty or over-256-symbol alphabet can loop forever instead of returning an ID.

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"

[nanoid-dictionary]: https://github.com/CyberAP/nanoid-dictionary

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.

import { customRandom, urlAlphabet } from "nanoid";
const nanoid = customRandom(urlAlphabet, 10, random);

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.

Non-Secure

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"

Note, that non-secure version is _slower_ than secure. Use it only if you have to.

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.

[useId]: https://react.dev/reference/react/useId

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";

[react-native-get-random-values]: https://github.com/LinusU/react-native-get-random-values

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(),
  …
})

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

TypeScript

Nano ID allows casting generated strings into opaque strings in TypeScript. For example:

declare const userIdBrand: unique symbol;
type UserId = string & { [userIdBrand]: true };
// Use explicit type parameter:
mockUser(nanoid<UserId>());
interface User {
  id: UserId;
  name: string;
}
const user: User = {
  // Automatically casts to UserId:
  id: nanoid(),
  name: "Alice",
};

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#
• C++
• Clojure and ClojureScript
• ColdFusion/CFML
• Crystal
• Dart & Flutter
• Elixir
• Gleam
• Go
• Haskell
• Haxe
• Janet
• Java
• Kotlin
• MySQL/MariaDB
• Nim
• OCaml
• Perl
• PHP
• Python native implementation

• Postgres Extension

• R (with dictionaries)
• Ruby
• Rust
• Swift
• Unison
• V
• Zig

[CLI]: #cli

Tools

• [ID size calculator] shows collision probability when adjusting

• [nanoid-dictionary] with popular alphabets to use with [customAlphabet].
• [nanoid-good] to be sure that your ID doesn’t contain any obscene words.