lock CSPRNG window.crypto.randomUUID() • Zero Server Generation RFC 9562

UUID & GUID Generator

Generate cryptographically secure v4 random UUIDs, monotonic time-ordered v7 identifiers for high-throughput relational databases, and custom legacy formats in browser memory.

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Collision Risk < 1 in 10³⁶ combinations

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Specification & Format

Local Web Crypto

Version Standard

Batch Quantity Max 100 per cycle

Encoding & Casing

Standard Hyphens 8-4-4-4-12 groups

Uppercase CAPITAL HEX

Enclosing Braces { ... } format

Base64 Encoded Compact 22 chars

Delimiter (Multi-Output)

Newlines (\n) Comma-Separated (, )

Sponsor: High-performance Cloud DB Engine

Primary Identifier Result 128-bit payload

e8b39d1b-3ef5-46b7-a37a-42c2be9fdce2

Cryptographic Strength 122 Bits Random Entropy

CSPRNG • 5.3×10³⁶ distinct states Zero client storage

Batch Stream

5 items

check_circle Ready to paste into Postgres, MySQL, MongoDB, JSON APIs UTF-8 / Plain

Bit-Level Specification

Anatomy of RFC 9562 UUIDv4 vs UUIDv7

UUIDs comprise exactly 128 bits represented as 32 hexadecimal digits divided by hyphens. Understanding bit assignments prevents subtle collision regressions.

time_low / rand_a 32 bits (8 hex) e8b39d1b

time_mid 16 bits (4 hex) 3ef5

ver (4 bits) + rand 16 bits (4 hex) 46b7 [v4]

var (2 bits) + rand 16 bits (4 hex) a37a

rand_b (node) 48 bits (12 hex) 42c2be9fdce2

MSB (Most Significant Bit - Bit 0) Total 128 Bits = 16 Octets LSB (Least Significant Bit - Bit 127)

B-Tree Fragmentation & Index Analysis

Choosing the Right Primary Key: UUIDv4 vs UUIDv7 vs ULID vs Snowflake

In high-write workloads, purely random keys (like UUIDv4) force random write I/O across database leaf pages, causing heavy page splits, buffer pool pollution, and cache invalidation.

UUIDv4 (Random) High Split

~42% Index Size

Severe leaf-page fragmentation in PostgreSQL B-Trees above 10M rows.

UUIDv7 (RFC 9562) Optimized

< 4% Overhead

Time-ordered sequential insertion keeps write buffers tightly clustered.

ULID Crockford

26 Chars

Base32 URL-safe string representation, 1.21e+24 unique values per ms.

Snowflake 64-bit Int

BIGINT

Requires coordinated cluster worker IDs; native hardware 64-bit comparisons.

Standard Identifier	Size / Type	Sortability	Random Bits	B-Tree Health	Best Application
UUID Version 4	128 bits (36 char)	Non-sequential	122 bits	Poor (Heavy page churn)	Public tokens, session IDs, opaque keys
UUID Version 7	128 bits (36 char)	Monotonic Time-order	74 bits	Excellent (Append only)	Modern RDBMS Primary Keys (Postgres, MySQL 8)
ULID	128 bits (26 char Base32)	Monotonic Time-order	80 bits	Excellent (Append only)	NoSQL documents, URL-safe path slugs
Twitter Snowflake	64 bits (BIGINT)	Monotonic Time-order	12 bits sequence	Optimal (Native 8-byte ints)	Massive distributed feeds, messaging events
UUID Version 1	128 bits (36 char)	Timestamp scrambled	0 (Node MAC based)	Moderate	Legacy systems (Leaked MAC privacy risk)

Engineering Documentation

Frequently Asked Questions

Is this generator safe for production secrets?

Yes. Identifiers are generated directly inside your active browser context via the Web Cryptography API (window.crypto.getRandomValues and randomUUID()). No string or seed ever transmits across the wire or touches external telemetry servers.

Why migrate from UUIDv4 to UUIDv7?

UUIDv4 distributes inserts completely at random across your B-tree index. When tables exceed physical RAM, each write requires reading random disk blocks into memory. UUIDv7 prefixes a 48-bit millisecond timestamp, assuring high-speed, sequential index writes without central coordination.

What is the exact collision probability of UUIDv4?

To reach a 50% probability of a single collision (birthday paradox), you would need to continuously produce 1 billion UUIDs every second for 85 years (approx. 2.71 × 10¹⁸ UUIDs). For distributed services, it is practically collision-immune.

Can I convert these UUIDs to binary columns?

Yes. Storing UUIDs as UUID in PostgreSQL or BINARY(16) in MySQL cuts storage by 55% compared to VARCHAR(36) and boosts query search speed.

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