Online UUID & GUID Generator
Generate secure UUID v4 and time-ordered UUID v7 identifiers online. Create single or bulk UUIDs with formatting controls, GUID support, and client-side Web Crypto generation.
Bulk UUID Generator
Up to 1,000 UUIDsOverview
The ToolMono UUID & GUID Generator is an enterprise-grade developer utility designed for distributed systems architects, database engineers, backend API developers, and security specialists. Universally Unique Identifiers (UUIDs) and Globally Unique Identifiers (GUIDs) are 128-bit numbers standardized by the IETF in RFC 9562 (updating RFC 4122). They allow independent computer systems to generate unique identifiers without consulting a central authority or database coordinator.
Traditional auto-incrementing integer IDs create massive bottlenecks in distributed microservices and leak business metrics (such as daily order volume) to public API consumers. By utilizing 128-bit UUIDs, distributed nodes can safely assign primary keys independently. However, random UUID v4 keys introduce severe database B-Tree index fragmentation when used as primary keys. The latest RFC 9562 standard formalizes UUID v7, embedding a 48-bit Unix millisecond timestamp at the front to guarantee sequential, time-sortable database insertions.
ToolMono executes 100% client-side UUID generation using your browser's native Web Crypto API (crypto.getRandomValues()). Whether you need random UUID v4s, time-sorted UUID v7s, legacy GUIDs without dashes, or bulk generation up to 10,000 records, your identifiers remain 100% private. For complementary developer workflows, explore our Timestamp Converter, Hash Generator, Random Generator, and JSON Formatter.
UUID & GUID Versions (RFC 9562 & RFC 4122)
RFC 9562 defines multiple UUID versions, each optimized for specific architectural use cases:
Embeds a 48-bit Unix millisecond timestamp + 74 bits of random entropy. The modern gold standard for database primary keys.
Uses 122 bits of pure cryptographic entropy. Ideal for general API keys, session tokens, and non-indexed identifiers.
v1 uses Gregorian 100ns timestamp + MAC address. v6 reorders v1 bits to make time high-bits sortable.
128-bit Globally Unique Identifier format used in C#, .NET, and SQL Server, formatted with optional braces or uppercase.
RFC 9562 version reserved for custom or experimental bit structures requiring proprietary timestamp layouts.
Bulk UUID Generation Engine
High-Performance Web Crypto Batch Processing
ToolMono allows developers to generate up to 10,000 UUIDs in a single instant batch using Web Crypto API hardware acceleration:
Virtualized Pagination
Renders massive lists smoothly without freezing your browser DOM.
Instant Search Filter
Filter through generated batches instantly by prefix or timestamp match.
Database Seeding Ready
Format output directly into SQL INSERT lists, JSON arrays, CSVs, or plain text.
Interactive UUID Inspector & Parser
Deep 128-Bit Dissection & Timestamp Decoding
ToolMono includes a full-featured UUID Inspector. Paste any UUID string to inspect its underlying structure:
UUID v7 Bit Layout Visualizer
RFC 9562 Bit Layout: 018f3a5e-23ba-79c2-9e8a-8b1e4f2c9d3a
UUID v7 structures its 128 bits into specific fields: Bits 0–47 contain a 48-bit Unix timestamp in milliseconds; Bits 48–51 specify Version 7 (0111); Bits 52–63 contain 12 bits of random entropy (Rand_A); Bits 64–65 specify the RFC 9562 Variant (10); and Bits 66–127 contain 62 bits of random entropy (Rand_B).
Database Guidance & B-Tree Indexing
Using random UUID v4 as primary keys in relational databases leads to severe performance penalties known as B-Tree Index Page Splits. Because v4 values arrive in random order, inserting a new record forces the database to write to random memory pages, causing frequent page splitting, buffer cache misses, and index bloat.
PostgreSQL Optimization
PostgreSQL stores UUIDs as a native 16-byte type. Switching to UUID v7 keeps inserts append-only at the rightmost leaf of the B-Tree index, improving insert throughput by up to 5x.
MySQL / InnoDB Clustered Keys
InnoDB clusters table data around the primary key. Random UUID v4 forces random disk I/O. UUID v7 ensures sequential primary key allocation, reducing storage overhead by 50%.
SQL Server UNIQUEIDENTIFIER
SQL Server's NEWID() is random v4. Use UUID v7 or NEWSEQUENTIALID() to prevent SQL Server clustered index fragmentation.
Code Examples (11 Languages)
Select your target programming language to view UUID generation code:
// 1. UUID v4 using Native Web Crypto API (Browser & Modern JS)
const uuidV4 = crypto.randomUUID();
console.log("UUID v4:", uuidV4);
// 2. UUID v7 Generation in JavaScript (Time-Sortable RFC 9562)
function generateUuidV7() {
const bytes = new Uint8Array(16);
crypto.getRandomValues(bytes);
const nowMs = Date.now();
// 48-bit Unix timestamp
bytes[0] = Math.floor(nowMs / 0x10000000000) & 0xff;
bytes[1] = Math.floor(nowMs / 0x100000000) & 0xff;
bytes[2] = Math.floor(nowMs / 0x1000000) & 0xff;
bytes[3] = Math.floor(nowMs / 0x10000) & 0xff;
bytes[4] = Math.floor(nowMs / 0x100) & 0xff;
bytes[5] = nowMs & 0xff;
// Set version 7 (0111) & variant (10xx)
bytes[6] = (bytes[6] & 0x0f) | 0x70;
bytes[8] = (bytes[8] & 0x3f) | 0x80;
const hex = Array.from(bytes, b => b.toString(16).padStart(2, '0')).join('');
return `${hex.slice(0,8)}-${hex.slice(8,12)}-${hex.slice(12,16)}-${hex.slice(16,20)}-${hex.slice(20)}`;
}
console.log("UUID v7:", generateUuidV7());RFC 9562 Reference & Benchmark Tables
1. UUID Version Feature Matrix (RFC 9562 & RFC 4122)
| Version | Generation Source | Time-Sortable? | Entropy / Random Bits | Best Use Case |
|---|---|---|---|---|
| UUID v7 | Unix Epoch ms + Random | Yes (Monotonic) | 74 bits | Database Primary Keys |
| UUID v4 | Cryptographic Random | No (Random) | 122 bits | API Keys, Tokens, Non-DB IDs |
| UUID v1 | Gregorian 100ns + MAC | Partial (Low-bits first) | 14-bit Clock Seq | Legacy Distributed Systems |
| UUID v6 | Reordered Gregorian v1 | Yes | 14-bit Clock Seq | v1 Migration to Time-Sortable |
2. Identifier Format Comparison (UUID v7 vs ULID vs KSUID vs Snowflake)
| Format | Size (Bits) | Representation | Standardization | Sortable? |
|---|---|---|---|---|
| UUID v7 | 128 bits | 36-char Hex (8-4-4-4-12) | IETF RFC 9562 Standard | Yes |
| ULID | 128 bits | 26-char Crockford Base32 | Community Spec | Yes |
| KSUID | 160 bits | 27-char Base62 | Segment Proprietary | Yes |
| Snowflake | 64 bits | Integer / String | Twitter Custom | Yes |
What is UUID & How Does It Work?
A UUID consists of 128 bits represented as 32 hexadecimal digits separated by hyphens. A Version 4 UUID contains 122 bits of pure cryptographic random entropy. The total number of possible v4 UUIDs is 2^122 (approximately 5.3 x 10^36). To achieve a 50% probability of a single collision, a system would need to generate 1 billion UUIDs per second continuously for over 85 years.
AI Overview Answers
What is UUID?
A UUID (Universally Unique Identifier) is a 128-bit string defined by RFC 9562 used to uniquely identify records across distributed systems without a central coordinator.
What is UUID v7?
UUID v7 is a time-sortable 128-bit identifier standardized in RFC 9562 that combines a 48-bit Unix millisecond timestamp with 74 bits of random entropy to optimize database B-Tree indexing.
Should databases use UUID v7?
Yes. UUID v7 eliminates database B-Tree index page splits and fragmentation caused by random UUID v4, improving insert speed by up to 500% while maintaining global uniqueness.
How to Use ToolMono UUID Generator
Select Version
Choose v7 for DB keys, v4 for random tokens, or GUID.
Choose Quantity
Select amount from 1 up to 10,000 per batch.
Set Format
Toggle hyphens, uppercase, braces, or SQL INSERT list.
Generate
Click Generate to render instantly via Web Crypto.
Copy / Export
Copy batch or download TXT, CSV, JSON, or SQL.
UUID Best Practices
Use UUID v7 for Relational Database Keys
Always default to UUID v7 when assigning primary keys in PostgreSQL, MySQL, or SQL Server to preserve clustered index insertion speed.
Store as 16-Byte Binary in Storage
Store UUIDs in database binary columns (e.g. PostgreSQL `UUID` or `BINARY(16)`) to cut storage overhead by 55% compared to string representation.
Common Errors & Fixes
B-Tree Index Page Splits
Inserting random UUID v4 into indexed columns causes heavy disk I/O. Switch your schema to UUID v7 time-sortable keys.
Insecure Random Generators (Math.random)
Never write custom UUID generators relying on Math.random(). Always use Web Crypto API `crypto.randomUUID()` for cryptographic security.
Tips & Tricks
SQL INSERT List Export
Need mock records for local database testing? Use the SQL INSERT List export format to copy SQL statements ready for Execution.
Timestamp Extraction
Paste any UUID v7 or v1 into the interactive UUID Inspector to extract the exact millisecond creation timestamp.
Frequently Asked Questions
Privacy & E-E-A-T Verification
100% Client-Side Privacy & Web Crypto Security
ToolMono operates under strict privacy guarantees. All UUID generation, bit parsing, and visual inspection execute 100% locally inside your web browser. No generated keys, settings, or database records are ever uploaded to remote servers or logged.
- Compliant with IETF RFC 9562 Specs
- Zero Network Server Uploads
- Native Browser Web Crypto API
- 100% Offline Capable
References & Standards
RFC 9562: Universally Unique IDentifiers (UUID)
Official IETF standard specification for UUID versions v1 through v8.
ITU-T X.667: Generation and Registration of Universally Unique Identifiers
International Telecommunication Union standard for global UUID uniqueness.
W3C Web Cryptography API (crypto.randomUUID)
W3C standard for browser-native CSPRNG v4 UUID generation.
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