CUID vs UUID vs ULID — Which Should You Use?

UUID v4 is the default choice for unique IDs, but ULID and CUID solve specific problems UUID doesn't handle well: sortability, compact representation, and URL-friendliness. Here is a direct comparison of all four formats so you can pick the right one without reading four separate documentation sites.

UUID v4 vs UUID v7 vs ULID vs CUID2 — Side by Side

Property	UUID v4	UUID v7	ULID	CUID2
Format	8-4-4-4-12 hex	8-4-4-4-12 hex	26 base32 chars	24 alphanumeric
Length	36 chars (with dashes)	36 chars	26 chars	24 chars (configurable)
Bits of randomness	122	74	80	~112+
Time-ordered	No	Yes (ms precision)	Yes (ms precision)	Partial (time prefix)
RFC standard	RFC 4122	RFC 9562	No	No
Database native type	Yes (PG, MSSQL)	PG 17+	No — store as text	No — store as text
URL-safe	With encoding	With encoding	Yes (uppercase base32)	Yes
Case-sensitive	No	No	No (case-insensitive)	Yes (lowercase)

When to Choose Each Format

UUID v4 — choose when:

• Your database has a native UUID type (PostgreSQL, SQL Server)
• You need RFC 4122 compliance
• Randomness and collision resistance are the primary concerns
• You want zero dependencies in most language environments
• The IDs are internal (not user-facing in URLs)

UUID v7 — choose when:

• You want UUID format compatibility (same 36-char representation)
• You need sequential ordering for better database index performance
• PostgreSQL 17+ (built-in uuidv7()) or using a uuid library that supports it

ULID — choose when:

• You need sortable IDs (ULIDs sort lexicographically in the same order they were created)
• You want a shorter, URL-safe representation than UUID
• You are building event-driven systems where temporal ordering matters

CUID2 — choose when:

• You are building user-facing IDs in URLs (shorter, clean alphanumeric)
• You want fingerprinting resistance (no MAC address, no predictable sequences)
• Your ecosystem is Node.js / JavaScript-first (official library: @paralleldrive/cuid2)

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Code Examples for Each Format

// UUID v4 — Node.js (no dependencies)
const id = crypto.randomUUID();
// '550e8400-e29b-41d4-a716-446655440000'

// UUID v7 — requires uuid package v9.0+
import { v7 as uuidv7 } from 'uuid';
const id = uuidv7();
// '01956b13-f000-7000-8000-000000000000' (time-ordered)

// ULID — npm install ulid
import { ulid } from 'ulid';
const id = ulid();
// '01ARZ3NDEKTSV4RRFFQ69G5FAV' (sortable, URL-safe)

// CUID2 — npm install @paralleldrive/cuid2
import { createId } from '@paralleldrive/cuid2';
const id = createId();
// 'clh3gfx0e0000jzrmn1b7m42c' (short, alphanumeric)

# Python equivalents
import uuid
uuid.uuid4()  # UUID v4

# UUID v7 — pip install uuid6
import uuid6
uuid6.uuid7()

# ULID — pip install python-ulid
from ulid import ULID
str(ULID())  # sortable time-ordered ID

Short UUID Alternatives — NanoID and Others

If your main concern is length (UUID at 36 chars feels verbose), NanoID is worth knowing:

Format	Length	Charset	Comparable collision to UUID v4
UUID v4	36 chars (16 bytes)	hex + dashes	122 bits random
NanoID (default)	21 chars	A-Za-z0-9_-	~126 bits (more entropy per char)
ULID	26 chars	base32	80 bits random + 48 bits time
CUID2 (default)	24 chars	a-z0-9	~112 bits

// NanoID — npm install nanoid
import { nanoid } from 'nanoid';
const id = nanoid();           // 21 chars — default length
const short = nanoid(10);      // 10 chars — shorter, less collision resistance

The safe recommendation for most new projects: UUID v7 if your database supports it, UUID v4 otherwise. Only switch to ULID/CUID/NanoID if you have a specific requirement (URL friendliness, sort order) that UUID doesn't meet. See our UUID version guide for more on v4 vs v7.

Frequently Asked Questions

Is ULID better than UUID for databases?

ULID has two advantages: it is sortable (newer ULIDs are always greater than older ones, improving index performance) and it is shorter (26 vs 36 characters). The downside: no native database type, no RFC standard, and you must store it as text. UUID v7 achieves the same sequential ordering while maintaining RFC compatibility and native database type support.

What is the difference between CUID and CUID2?

CUID (v1) was deprecated due to fingerprinting vulnerabilities — the time component and process ID were predictable. CUID2 uses a cryptographic hash and removes fingerprinting. Always use @paralleldrive/cuid2, not the original cuid package.

Can I use ULID as a UUID primary key?

You can store a ULID in a UUID column by converting it to UUID format (some ULID libraries support this). But it is usually cleaner to store ULIDs as CHAR(26) or TEXT, or to use UUID v7 if sequential ordering is your goal — v7 is native UUID format with built-in time ordering.