Last Updated: 3/12/2026

Custom Alphabet & Size

Nanoid allows you to customize both the character set (alphabet) and default ID size using customAlphabet.

Basic Custom Alphabet

Create a custom ID generator with your own alphabet and size:


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

This creates a function that generates 10-character IDs using only hexadecimal characters.

You can override the default size when calling the function:


const nanoid = customAlphabet('1234567890abcdef', 10)
const shortId = nanoid(5) //=> "f01a2"

For environments without hardware random generators, use the non-secure version:


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

Important: Alphabets must contain 256 symbols or less. Larger alphabets compromise the internal generator’s security guarantees.

Always verify your custom alphabet and ID size in the ID collision calculator to ensure adequate collision resistance.

Numeric only:


const nanoid = customAlphabet('0123456789', 12)

Lowercase alphanumeric:


const nanoid = customAlphabet('abcdefghijklmnopqrstuvwxyz0123456789', 16)

No ambiguous characters (removes 0, O, I, l):


const nanoid = customAlphabet('123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz', 21)

For more alphabet options, check out nanoid-dictionary.

If you want to use the default URL-safe alphabet with customRandom:


import { customRandom, urlAlphabet } from 'nanoid'
 
const nanoid = customRandom(urlAlphabet, 10, customRandomFunction)