What is the difference between UUID v4 and UUID v7?

UUID v4 consists of 122 bits of pure pseudorandom data with no order or timestamp. Because its values are completely scattered, inserting UUID v4 keys into database B-Tree indexes forces frequent page splits and heavy disk write amplification. In contrast, UUID v7 embeds the creation timestamp in its first 48 bits, allowing databases to append records sequentially to the end of index leaf nodes for up to 4x faster inserts.

Can two UUID v7 identifiers collide if generated at the exact same millisecond?

The collision probability is astronomically low. Even if two UUID v7 identifiers are generated in the exact same millisecond on two servers on opposite sides of the world, each identifier still contains 74 bits of cryptographically secure random entropy. You would need to generate hundreds of billions of IDs within the same millisecond before approaching a 50% probability of collision.

Can I extract the creation date from a UUID v7 identifier?

Yes! The first 12 hexadecimal characters of a UUID v7 represent the 48-bit Unix timestamp in milliseconds. Our built-in 'Inspect & Decode' tab automatically parses this timestamp and displays both the exact UTC time and your local browser time down to the millisecond.

Are UUIDs generated on this site private and secure?

Yes, 100%. All UUIDs are generated directly inside your web browser using the native Web Cryptography API (crypto.getRandomValues). Zero identifiers or inputs are transmitted to our servers or stored in any database.

Utility #14RFC 9562 & CSPRNG

UUID v4 & UUID v7 Generator

Generate bulk UUID v4 and modern time-sortable UUID v7 identifiers with custom formatting (hyphens, uppercase, quotes, SQL IN). Inspect and decode embedded timestamps instantly. 100% in-browser CSPRNG.

CSPRNG Engine Active|100% Client-Side

UUID Specification Version

Time-ordered 48-bit timestamp + 74 bits randomness. Ideal for PostgreSQL, MySQL, and B-Tree indexes.

Batch Quantity

Hyphens ('-')

Uppercase

Enclosure

Delimiter Format

Generated UUIDs List

Click any row to copy or inspect

101a0edd8-4f37-7a20-b5c6-a00507ec9320

15:46:11.383

201a0edd8-4f38-728c-bcc2-c4f51f1cafc7

15:46:11.384

301a0edd8-4f38-77e5-bdae-640b6130d600

15:46:11.384

401a0edd8-4f38-7b7d-8ea0-b28611e62e09

15:46:11.384

501a0edd8-4f38-71b5-95f2-d31624d8ef61

15:46:11.384

RFC 9562 UUID v7

Modern time-ordered 48-bit millisecond timestamps preventing PostgreSQL, MySQL, and SQLite B-tree index fragmentation.

Classic UUID v4

122 bits of cryptographically secure pseudo-random entropy generated via the native Web Crypto API.

Timestamp Decoder

Paste any UUID v7 or v1 string to instantly recover the exact creation date, UTC timestamp, and local browser time.

100% In-Browser Privacy

Identifiers are generated in client memory. No backend network requests, zero telemetry, and zero tracking logs.

Engineering Guide: Why Databases Are Migrating to UUID v7

How the 128-bit structure of UUID v7 solves the performance issues of UUID v4 and ULID in distributed architectures.

1. The B-Tree Fragmentation Dilemma

Relational databases (PostgreSQL, MySQL InnoDB, CockroachDB) organize primary keys using B-Tree indexes. When using UUID v4, new keys arrive in completely random alphabetical order, causing continuous page splits and cache churn.

2. Natural Time-Order Append

Because UUID v7 embeds a 48-bit millisecond timestamp as its highest-order bits, every newly created ID is naturally greater than the last. Inserts append neatly to the rightmost leaf of the B-Tree, reducing write amplification by up to 75%.

3. Standardized 128-Bit Compatibility

Unlike ULID or NanoID which require custom varchar columns, UUID v7 is an official RFC standard that fits natively inside standard database `uuid` binary columns (16 bytes), maintaining full ORM and driver compatibility.

Frequently Asked Questions About UUIDs

Technical answers regarding RFC 9562, UUID v4 vs v7, database performance, and collision safety.

Ratified by the IETF in May 2024, RFC 9562 officially standardized UUID Version 7 to address the database performance pitfalls of random UUID v4. UUID v7 combines a 48-bit big-endian Unix timestamp (in milliseconds) with 74 bits of cryptographically secure pseudorandom entropy. This makes UUID v7 monotonically time-sortable while retaining universal uniqueness.