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UUID Generator Online: Generate v4, v1, and v7 UUIDs Instantly Free

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UUID Generator Online: Generate v4, v1, and v7 UUIDs Instantly Free

UUIDs (Universally Unique Identifiers) are the standard way to generate unique IDs without a central authority. Whether you're seeding a database, testing an API, or generating session tokens, an online UUID generator gives you ready-to-use identifiers in seconds.

This guide covers the UUID versions, when to use each, and how to generate them in code.

What Is a UUID?

A UUID is a 128-bit identifier formatted as a 36-character string:

xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx

Example: f47ac10b-58cc-4372-a567-0e02b2c3d479
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  • 32 hexadecimal digits
  • 4 hyphens separating 5 groups (8-4-4-4-12 characters)
  • The M position indicates the version; N indicates the variant

Try it now: DevPlaybook UUID Generator — generate single or bulk UUIDs in any version instantly.

UUID Versions Explained

UUID v4 (Random) — Most Common

UUID v4 uses 122 random bits. The probability of generating two identical UUIDs is astronomically low — roughly 1 in 5.3 × 10^36.

f47ac10b-58cc-4372-a567-0e02b2c3d479
              ^                      ← "4" indicates v4
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Use when: You need unique IDs that don't encode any information about creation time or source. Best for primary keys, session tokens, resource identifiers.

UUID v1 (Time-Based) — Contains MAC Address

UUID v1 embeds the current timestamp (100-nanosecond intervals since Oct 15, 1582) and the MAC address of the generating machine.

6ba7b810-9dad-11d1-80b4-00c04fd430c8
              ^                      ← "1" indicates v1
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Use when: You need UUIDs that sort roughly by creation time. Avoid for privacy — the MAC address reveals the generating machine.

UUID v7 (Time-Ordered) — Modern Recommended

UUID v7 combines a Unix timestamp (millisecond precision) with random bits. This makes them monotonically increasing, which is much better for database indexes than random v4 UUIDs.

018e5716-a2a0-7b4e-8f5c-d9f3b1e67a2c
^^^^^^^^^^^^^^^                      ← first 48 bits = timestamp
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Use when: You want database-friendly IDs that sort by creation time. UUID v7 provides the uniqueness of v4 with the sortability of auto-increment integers.

UUID v4 vs UUID v7: Which Should You Use?

Factor UUID v4 UUID v7
Randomness 122 random bits ~74 random bits
Sortable by time ❌ No ✅ Yes
Database index efficiency ⚠️ Poor (random insertions) ✅ Good (sequential inserts)
Privacy ✅ No metadata ✅ No MAC address
Browser support ✅ crypto.randomUUID() ⚠️ Library required
Recommended for new projects ✅ Widely supported ✅ Better for databases

For most web applications in 2026, UUID v7 is the recommended choice for database primary keys. Use v4 when you need broader library support or don't care about insert performance.

How to Use the UUID Generator Online

  1. Open DevPlaybook UUID Generator
  2. Select the UUID version (v4, v1, v7)
  3. Choose how many UUIDs you need (1 to bulk)
  4. Select format — standard hyphenated, compact (no hyphens), uppercase
  5. Click Generate
  6. Copy the UUIDs for use in seeds, test fixtures, API testing

Generating UUIDs in Code

JavaScript / Node.js 

// v4 — built into modern environments (no library needed)
const uuid = crypto.randomUUID();
// "f47ac10b-58cc-4372-a567-0e02b2c3d479"

// v4 — older Node.js or browser compatibility
import { v4 as uuidv4 } from 'uuid';
console.log(uuidv4());

// v7 — requires library
import { v7 as uuidv7 } from 'uuid';
console.log(uuidv7());
// "018e5716-a2a0-7b4e-8f5c-d9f3b1e67a2c"
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Python 

import uuid

# v4
id = str(uuid.uuid4())
# "f47ac10b-58cc-4372-a567-0e02b2c3d479"

# v1
id = str(uuid.uuid1())

# As a compact string (no hyphens)
compact = str(uuid.uuid4()).replace('-', '')
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Go 

import "github.com/google/uuid"

// v4
id := uuid.New()
fmt.Println(id.String())

// v7
id, err := uuid.NewV7()
fmt.Println(id.String())
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SQL 

-- PostgreSQL: generate UUID v4
SELECT gen_random_uuid();

-- PostgreSQL: UUID as default column value
CREATE TABLE users (
    id UUID DEFAULT gen_random_uuid() PRIMARY KEY,
    name TEXT NOT NULL
);

-- MySQL 8+
SELECT UUID();

-- SQLite (no built-in, use application layer)
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UUIDs as Database Primary Keys

The Problem with Auto-Increment

Auto-increment integers work well for small, single-database applications but break down when:

  • You need to merge datasets from multiple sources
  • You generate IDs before they're committed to the database (offline-first)
  • You're running multiple database instances
  • You don't want to expose record counts to users via guessable IDs

UUID Trade-offs 

-- UUID v4: random insertions cause index fragmentation
INSERT INTO users (id, name) VALUES (gen_random_uuid(), 'Alice');
-- Every insert potentially goes to a different B-tree page

-- UUID v7: sequential inserts are index-friendly
-- New records always append to the end of the index
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For high-write-throughput systems, UUID v7 or ULIDs can provide the best of both worlds.

UUID Validation

A valid UUID matches this regex pattern:

^[0-9a-f]{8}-[0-9a-f]{4}-[1-8][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$
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Quick JavaScript validation:

function isValidUUID(str) {
  return /^[0-9a-f]{8}-[0-9a-f]{4}-[1-8][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i.test(str);
}
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Frequently Asked Questions

Can two UUIDs ever be identical?

In theory, yes — they're random. In practice, no — the probability of collision is so small (1 in 5.3 × 10^36 for v4) that it's not a realistic concern for any application. You'd need to generate approximately 2.7 quintillion UUIDs before having a 50% chance of even one collision.

Should I store UUIDs as strings or binary in databases?

Binary (16 bytes) is more efficient than string (36 bytes). PostgreSQL's native UUID type stores it as 16 bytes. MySQL BINARY(16) is more efficient than VARCHAR(36). If storage efficiency matters, use the native type.

What's a ULID and how is it different from UUID?

ULID (Universally Unique Lexicographically Sortable Identifier) is a UUID alternative with 128 bits: 48-bit timestamp + 80-bit randomness. Like UUID v7, it's sortable. The difference is ULIDs use a different character set (Crockford Base32) for a more compact 26-character string vs UUID's 36 characters.

Are UUIDs case-sensitive?

No. F47AC10B-58CC-4372-A567-0E02B2C3D479 and f47ac10b-58cc-4372-a567-0e02b2c3d479 are the same UUID. Convention is lowercase. Use lowercase unless your system requires otherwise.

Can I use a UUID as an API key?

You can, but it's not ideal. UUIDs are not designed for security — they're just unique, not secret in the same way. For API keys, use a cryptographically random value (e.g., 32 random bytes encoded as hex or base64) and optionally prefix it with a service identifier (e.g., sk_live_).

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