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Generate UUID v7

Generate a Unix timestamp-based UUID v7 with millisecond precision, ideal for database primary keys.

Code

Utilities
const t = Date.now().toString(16).padStart(12, '0');
const r = crypto.getRandomValues(new Uint8Array(10));
r[0] = (r[0] & 0x0f) | 0x70;
r[2] = (r[2] & 0x3f) | 0x80;
const h = Array.from(r, b => b.toString(16).padStart(2, '0')).join('');
return `${t.slice(0, 8)}-${t.slice(8)}-${h.slice(0, 4)}-${h.slice(4, 8)}-${h.slice(8)}`;
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What is UUID v7?

UUID v7 is the modern standard for time-based UUIDs. It combines a Unix timestamp in milliseconds with random bits, designed specifically for database primary keys.

018e5c4d-a8b0-7123-abcd-1234567890ab ├────────────┤ ↑ 48-bit ms version 7 timestamp

Why UUID v7 is the Best Choice for Databases

1. Naturally Sortable

UUIDs generated later are always lexicographically greater:

uuid_v7() // "018e5c4d-0000-7..." (earlier)
uuid_v7() // "018e5c4d-0001-7..." (later - sorts after!)

2. B-tree Friendly

Random UUIDs (v4) cause index fragmentation — new records insert randomly throughout the tree. v7's sequential nature means new records append to the end, dramatically improving:

  • Insert performance
  • Index size
  • Cache efficiency

3. Embeds Creation Time

Extract the timestamp without a database query:

const uuid = "018e5c4d-a8b0-7123-abcd-1234567890ab";
const timestamp = parseInt(uuid.replace(/-/g, '').slice(0, 12), 16);
new Date(timestamp); // → 2024-03-15T10:30:00.000Z

UUID v7 vs Others

VersionBest For
v4Security-sensitive IDs, no time needed
v7Database PKs, event logs, anything needing sort order
v5Deterministic IDs from names
v1/v6Legacy compatibility

Database Performance Comparison

MetricUUID v4UUID v7Auto-increment
Insert speedSlow (random)Fast (sequential)Fastest
Index sizeLargerSmallerSmallest
Distributed generationYesYesNo
Information leakageNoneTimestampRecord count

The Recommendation

For new projects using UUIDs as primary keys, use v7. It gives you the distributed generation benefits of UUIDs with the database performance closer to auto-increment IDs.

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