The Complete NanoID Guide: Tiny, Secure, URL-Friendly Unique IDs

When you need a unique identifier in a modern application, the UUID has long been the default choice. But UUIDs are verbose (36 characters), require URL encoding when placed in links, and carry around more string than most use cases actually need. NanoID is a tiny, secure, and URL-friendly alternative that has quietly become one of the most popular ID libraries in the JavaScript ecosystem.

In this guide, we'll break down what NanoID is, why it's often a better fit than UUID, and how to generate your own using our free NanoID Generator.

What is NanoID?

NanoID is a small, secure, URL-friendly unique string ID generator. By default, it produces a 21-character string using an alphabet of 64 URL-safe symbols:

A-Za-z0-9_-

A typical NanoID looks like this:

V1StGXR8_Z5jdHi6B-myT

That compact string packs 126 bits of entropy, which is the same collision resistance as a standard 128-bit UUID (a couple of bits are traded for the smaller alphabet). At this size, the probability of a collision is roughly one in a trillion when generating IDs at scale — meaning you can generate around 151 million IDs per second for a year and still have a negligible chance of a duplicate. For virtually every application, NanoID is as collision-proof as a UUID, just shorter.

Why Use NanoID Instead of UUID?

NanoID was designed to fix the practical annoyances of UUIDs while keeping their uniqueness guarantees. Here's why developers reach for it:

1. Compactness

A default NanoID is 21 characters, while a UUID v4 is 36 characters (including hyphens). That's roughly 40% shorter, which saves bytes in URLs, database rows, log files, and network payloads — savings that compound quickly when IDs appear millions of times.

2. URL-Safe by Default

NanoID uses only A-Za-z0-9_-, characters that are legal in URLs without encoding. UUIDs contain hyphens that are fine, but tools sometimes mishandle them, and any custom format with / or + forces percent-encoding. NanoIDs drop cleanly into path segments, query strings, and HTML attributes.

3. Faster Generation

NanoID uses a larger alphabet (64 symbols vs. UUID's 16 hex digits), so it needs fewer bytes from the random number generator to reach the same entropy. Less RNG work means faster generation, especially at high volumes.

4. Customizable Alphabet and Size

Unlike UUID's rigid format, NanoID lets you define your own alphabet (for example, to add a prefix or strip out ambiguous characters like 0, O, l, and 1) and choose any length you want.

5. Built on Cryptographic Randomness

NanoID sources its randomness from the platform's secure RNG — the Web Crypto API (crypto.getRandomValues) in browsers and crypto.randomBytes in Node.js. It does not rely on Math.random().

NanoID vs UUID v4 at a Glance

Key Features of NanoID

• Compact: 21-character default, about 40% shorter than a UUID.
• URL-safe: Uses only _- and alphanumeric characters — no percent-encoding needed.
• Customizable alphabet: Add prefixes, remove ambiguous characters, or restrict to a specific set.
• Adjustable length: Default is 21, but any size from 1 to 100 (and beyond) is supported.
• Secure randomness: Uses the Web Crypto API / crypto.randomBytes under the hood.
• Tiny library: The core package is around 130 bytes minified and gzipped.
• Available everywhere: Official and community ports exist for JavaScript, Python, Go, Rust, Java, C#, Swift, PHP, Ruby, and more.

How to Use Our NanoID Generator

Generating IDs in your browser takes seconds — no install required.

1. Open the tool: Head to the NanoID Generator.
2. Set the size: Choose how long each ID should be, from 1 to 100 characters (21 is the default).
3. Customize the alphabet (optional): Use the default URL-safe set or define your own to add a prefix or drop ambiguous characters.
4. Pick the quantity: Generate up to 100 NanoIDs in a single batch.
5. Generate and copy: Hit generate, then copy any ID (or the whole list) with one click.

NanoID vs Other ID Formats

How does NanoID stack up against the alternatives?

• NanoID vs UUID: Both offer ~1-in-a-trillion collision safety. NanoID wins on size (21 vs 36 chars) and URL-safety; UUID wins on universal familiarity and strict formatting standards.
• NanoID vs ULID: ULIDs are 26 characters and lexicographically sortable by timestamp, making them ideal for database indexes. NanoIDs are shorter and faster but not sortable — choose NanoID for compactness, ULID for ordered data. Try our ULID Generator for sortable IDs.
• NanoID vs auto-increment: Auto-increment integers are tiny and sortable but require a central database, leak row counts, and don't work across distributed services. NanoIDs are generated independently on any node with no coordination.

Generating NanoIDs in Code

NanoID has first-class libraries in every major language. Here are the most common.

JavaScript / Node.js:

import { nanoid, customAlphabet } from 'nanoid';

// Default: 21-character URL-safe ID
console.log(nanoid()); // => "V1StGXR8_Z5jdHi6B-myT"

// Custom size
console.log(nanoid(10)); // => "IRFa-Ya9oR"

// Custom alphabet (e.g. no ambiguous characters, with a prefix)
const customNanoID = customAlphabet('0123456789ABCDEF', 12);
console.log(customNanoID()); // => "5A4F2B9C1E7D"

Python:

from nanoid import generate

# Default 21-character ID
print(generate())  # => "V1StGXR8_Z5jdHi6B-myT"

Go:

import (
    "fmt"
    gonanoid "github.com/matoous/go-nanoid/v2"
)

func main() {
    id, _ := gonanoid.New()
    fmt.Println(id) // => "V1StGXR8_Z5jdHi6B-myT"
}

Common Use Cases

• Database primary keys: Compact, collision-safe keys for Postgres, MySQL, SQLite, and NoSQL stores.
• Shareable URLs: Short, safe slugs for documents, files, and public links.
• Session and token IDs: Unique handles for sessions, API tokens, or reset links.
• Frontend component keys: Stable keys for list items without leaking array indices.
• API request correlation IDs: Trace requests across microservices without a central allocator.
• Testing fixtures: Generate throwaway unique values for unit and integration tests.

Best Practices

• Stick with the default size unless you have a reason. 21 characters gives 126 bits of entropy — more than enough for virtually all apps.
• Use custom alphabets to add prefixes. Prefixing IDs (e.g. user_, order_) improves debuggability and lets you scan logs at a glance.
• Don't roll your own RNG. Always rely on crypto.getRandomValues or crypto.randomBytes — Math.random() is not cryptographically secure.
• Store the raw string. There's no need to normalize, lowercase, or re-encode a NanoID.
• Benchmark collisions for very high-volume systems. If you generate billions of IDs, compute the expected collision probability for your chosen length and bump the size if the margin feels too thin.

Conclusion

NanoID gives you the uniqueness guarantees of a UUID in a package that's 40% smaller, URL-safe by default, and blazing fast to generate. Whether you're building a database schema, a URL shortener, or a distributed backend, it's a modern default that's hard to beat.

Ready to try it? Generate your first batch of compact, secure IDs with our free NanoID Generator.

Related Tools:

• UUID Generator: Create standard UUIDs when you need a widely recognized 128-bit identifier format.
• ULID Generator: Generate lexicographically sortable IDs optimized for database indexing.
• Base64 Encoder/Decoder: Convert IDs and other data to or from Base64 strings.