UUIDv7 vs UUIDv4: A Complete Comparison

Universally Unique Identifiers (UUIDs) are 128-bit values used to identify records across distributed systems without coordination. For over a decade, UUIDv4 -- fully random identifiers -- has been the default choice. But in 2024, UUIDv7 emerged as a modern alternative defined in RFC 9562, embedding a Unix timestamp for chronological ordering. Which should you use? Let's compare them across every dimension that matters.

At a Glance

Detailed Comparison

Database Performance: Why It Matters

The most impactful difference between UUIDv4 and UUIDv7 is their behavior as database primary keys. Most databases use B-tree indexes for primary keys, and the insertion pattern of UUIDs directly affects index efficiency.

Uniqueness and Collision Resistance

UUIDv4 has 122 random bits, which means you would need to generate approximately 2.71 quintillion UUIDs to have a 50% chance of a collision (the birthday paradox). In practical terms, generating 1 billion UUIDs per second would take about 85 years before a collision becomes likely.

UUIDv7 has fewer random bits (62), but its uniqueness model is different. Because UUIDs generated at different milliseconds have different timestamp prefixes, collisions can only occur between UUIDs generated in the same millisecond. With 62 random bits per millisecond window, you would need to generate about 2.15 billion UUIDs in a single millisecond for a 50% collision probability -- far beyond any realistic workload.

Both versions provide more than sufficient uniqueness for any practical application. The theoretical difference in random bits is not a meaningful concern in the real world.

When to Use Each Version

Code Examples: Generating Both Versions

// UUIDv4 -- built-in since Node 14+
const v4 = crypto.randomUUID();
// "550e8400-e29b-41d4-a716-446655440000"

// UUIDv7 -- Node.js 20+ or use a library
// npm install uuidv7
import { uuidv7 } from "uuidv7";
const v7 = uuidv7();
// "01936b2e-1e85-7000-8000-4a6f7e3b2c1d"

// Extract timestamp from UUIDv7
function getTimestamp(uuid) {
  const hex = uuid.replace(/-/g, "").slice(0, 12);
  return new Date(parseInt(hex, 16));
}
console.log(getTimestamp(v7));
// 2024-12-01T10:30:45.000Z

import uuid

# UUIDv4 -- built-in
v4 = uuid.uuid4()
# UUID('550e8400-e29b-41d4-a716-446655440000')

# UUIDv7 -- Python 3.x with uuid7 library
# pip install uuid7
from uuid_extensions import uuid7
v7 = uuid7()
# UUID('01936b2e-1e85-7000-8000-4a6f7e3b2c1d')

# Extract timestamp from UUIDv7
def get_timestamp(uuidv7: str) -> int:
    hex_str = str(uuidv7).replace('-', '')[:12]
    return int(hex_str, 16)

from datetime import datetime
ts_ms = get_timestamp(str(v7))
print(datetime.utcfromtimestamp(ts_ms / 1000))

-- UUIDv4 (all PostgreSQL versions)
SELECT gen_random_uuid();
-- 550e8400-e29b-41d4-a716-446655440000

-- UUIDv7 (PostgreSQL 17+)
SELECT gen_random_uuid_v7();
-- 01936b2e-1e85-7000-8000-4a6f7e3b2c1d

-- Using UUIDv7 as a sortable primary key
CREATE TABLE events (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid_v7(),
  name TEXT NOT NULL,
  created_at TIMESTAMPTZ DEFAULT now()
);
-- IDs are naturally ordered by creation time

import "github.com/google/uuid"

// UUIDv4
v4 := uuid.New()

// UUIDv7
v7, _ := uuid.NewV7()

// Extract timestamp from UUIDv7
ts, _ := uuid.TimestampFromV7(v7)
sec, nsec := ts.Time().Unix(), ts.Time().Nanosecond()

Internal Structure Comparison

Frequently Asked Questions