UUID vs NanoID Comparison

NanoID is a compact, URL-safe unique identifier generator created by Andrey Sitnik in 2017. It prioritizes small size and URL-friendliness over standardization, making it a popular choice for frontend applications and short URLs.

Key differences:

Property	UUID v4	NanoID (default)
Length	36 chars	21 chars
Alphabet	Hex + hyphens	A-Za-z0-9_-
Bits of entropy	122	126
URL safe	No (needs encoding)	Yes
Standard	RFC 9562	Community spec
Sortable	No	No

NanoID's alphabet: The default alphabet uses 64 characters (A-Za-z0-9_-), which means each character encodes 6 bits. With 21 characters, NanoID provides 126 bits of entropy — slightly more than UUID v4's 122 bits, in a string that is 15 characters shorter.

Collision probability: Both UUID v4 and NanoID (default settings) have negligible collision probability for all practical purposes. You would need to generate IDs at a rate of 1,000 per second for approximately 149 billion years to reach a 1% collision probability with NanoID's default settings.

Customization: NanoID's biggest advantage is configurability. You can adjust both the alphabet and the length:

import { customAlphabet } from 'nanoid';

// Numeric-only IDs (for order numbers, etc.)
const numericId = customAlphabet('0123456789', 12);
numericId(); // "839102748561"

// Short IDs for URLs
const shortId = customAlphabet('abcdefghijklmnopqrstuvwxyz', 10);
shortId(); // "kbrmpfhqvx"

This flexibility is something UUIDs do not offer — a UUID is always 128 bits in a fixed hex format.

Size comparison in different contexts:

• In a URL: /items/V1StGXR8_Z5jdHi6B-myT (NanoID) vs /items/550e8400-e29b-41d4-a716-446655440000 (UUID)
• In a JSON payload with 1000 IDs: NanoID saves ~15 KB of raw text
• In binary storage: Both can be stored in 16 bytes, but NanoID requires custom encoding

When NOT to use NanoID: Avoid NanoID when you need database-native UUID support, time-ordered IDs (use UUID v7 instead), interoperability with systems that expect UUIDs, or when you need to extract metadata from the ID (version, timestamp).

Bundle size: NanoID is famously tiny at approximately 130 bytes (minified + gzipped), making it ideal for frontend applications where bundle size matters.