NanoID

NanoID is a tiny, secure, URL-friendly unique string ID generator. It’s designed to be compact while maintaining sufficient uniqueness for most use cases.

Overview

Format

V1StGXR8_Z5jdHi6B-myT
|---------------------|
  21 random characters

Example: V1StGXR8_Z5jdHi6B-myT

Characteristics

URL-Safe

The default alphabet is URL-safe:

A-Za-z0-9_-

No encoding needed when used in URLs.

Compact

At 21 characters, NanoID is shorter than UUID (36 chars) and ULID (26 chars).

Customizable

Both alphabet and length can be customized:

# Custom length
idt gen nanoid --length 32

# Custom alphabet
idt gen nanoid --alphabet "0123456789abcdef"

# Both
idt gen nanoid --length 16 --alphabet "ABCDEFGHIJKLMNOP"

Secure

Uses cryptographically secure random number generation.

Generation

# Default NanoID (21 characters)
idt gen nanoid

# Longer NanoID
idt gen nanoid --length 32

# Multiple NanoIDs
idt gen nanoid -n 10

Custom Alphabets

# Hex characters only
idt gen nanoid --alphabet "0123456789abcdef"

# Numbers only
idt gen nanoid --alphabet "0123456789"

# Lowercase letters only
idt gen nanoid --alphabet "abcdefghijklmnopqrstuvwxyz"

# Alphanumeric (no special chars)
idt gen nanoid --alphabet "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"

Inspection

$ idt inspect V1StGXR8_Z5jdHi6B-myT
NANOID
  V1StGXR8_Z5jdHi6B-myT

  Hex        ...
  Base64     ...

Note: NanoID doesn’t embed timestamps or other structured data.

Collision Probability

With default settings (21 characters, 64-character alphabet):

• ~126 bits of entropy
• For 1% collision probability: ~149 billion IDs
• For 50% collision probability: ~2.4 trillion IDs

Adjusting for Your Needs

Use this formula to calculate collision probability:

bits = log2(alphabet_size) * length

Examples:

• 21 chars, 64 alphabet: ~126 bits
• 32 chars, 64 alphabet: ~192 bits
• 16 chars, 16 alphabet (hex): ~64 bits

Comparison with Other IDs

*UUIDv7 has timestamp and sortability

When to Use NanoID

Good for:

• Short, URL-friendly IDs
• Client-side ID generation
• Non-sequential IDs (no ordering needed)
• Custom ID formats

Consider alternatives if:

• You need time-sortable IDs (use ULID or UUIDv7)
• You need to extract timestamps (use ULID or UUIDv7)
• You need distributed coordination (use Snowflake)
• You need UUID compatibility (use UUID)

Common Configurations

API Keys

# Long, alphanumeric
idt gen nanoid --length 32 --alphabet "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"

Short Codes

# 8-character codes (for sharing)
idt gen nanoid --length 8

Numeric IDs

# Numeric only (for phone-friendly codes)
idt gen nanoid --length 6 --alphabet "0123456789"

Specification

• GitHub: https://github.com/ai/nanoid
• Collision calculator: https://zelark.github.io/nano-id-cc/