UUID v7 Generator

UUID v7 is the modern, time-ordered UUID — a Unix millisecond timestamp followed by random bits. The right primary key for new tables.

Why v7 changed the game

For two decades, advice on UUIDs as primary keys went: "don't, they fragment your index." That was true for v4. v7 fixes it. The first 48 bits are a millisecond timestamp, so consecutive UUIDs cluster together in B-tree storage — the same access pattern as a bigint identity column.

Bit layout

┌─────────────────────────────────────────────────────────────────┐
│  48-bit Unix ms timestamp │ ver │ 12-bit rand │ var │ 62-bit rand│
└─────────────────────────────────────────────────────────────────┘
        most significant ──────────────────►  least significant

Real-world impact

A 100M-row PostgreSQL table with v4 primary keys typically inserts ~2–5× slower than the same table with v7 keys, because each insert has to read and write a different B-tree leaf page. v7's locality reduces that to near-sequential I/O.

Code

// JavaScript / TypeScript
import { v7 } from "uuid";
v7(); // "01928a47-3b30-7c5e-9d1a-f0b8c4a7e923"

// PostgreSQL 18+
SELECT uuidv7();

// Python (uuid-utils)
from uuid_utils import uuid7
uuid7()

When NOT to use v7

• When the timestamp must not be visible (privacy-sensitive IDs).
• When you need strict monotonic ordering across processes — v7 only guarantees per-process order; clock skew between hosts can interleave UUIDs.