UUID / GUID Generator & Inspector
/generate/RFC 4122 v4 & RFC 9562 v7 · Bulk Export · 100% In-Browser Privacy
What is a UUID / GUID and Why Does It Matter in Database Architecture?
A Universally Unique Identifier (UUID)—also known as a Globally Unique Identifier (GUID) in Microsoft ecosystems—is a 128-bit label used for information in computer systems. Standardized by RFC 4122, a canonical UUID is rendered as 32 hexadecimal characters separated by four hyphens into an 8-4-4-4-12 format (totaling 36 characters including hyphens).
Because there are $2^122 \approx 5.3 \times 10^36$ possible random UUID v4 combinations, the probability of generating a duplicate key across distributed microservices or multi-master databases is effectively zero. In practical terms, you would need to generate 1 billion UUIDs every second for 85 years before experiencing a 50% chance of a single collision.
UUID Version 4 (Random)
The industry standard for primary keys. Created using cryptographically strong pseudo-random numbers (CSPRNG), making key values completely unpredictable and secure against sequential enumeration attacks.
UUID Version 7 (Time-Ordered)
The modern RFC 9562 standard. Encodes a 48-bit Unix epoch millisecond timestamp at the beginning, followed by random bytes. Eliminates B-Tree index fragmentation in PostgreSQL, MySQL, and SQLite.
How to Generate and Inspect UUIDs
- Select your version: Choose UUID v4 for standard random keys or UUID v7 for timestamp-ordered database indexes.
- Choose quantity: Select from 1 up to 100 UUIDs per generation batch.
- Configure syntax: Toggle uppercase letters, hyphens, enclosing braces (
{...}), or format as a JSON Array (["..."]) or SQLIN (...)clause. - Copy or export: Click Copy All Output, or download as a
.txtor.jsonfile. - Inspect existing UUIDs: Paste any UUID into the Inspector card on the left to verify its RFC version and validity.
Frequently Asked Questions (FAQ)
Is there any difference between a UUID and a GUID? ↓
Functionally, they are identical 128-bit identifiers. "UUID" is the open standard term defined by ISO/IEC 11578 and RFC 4122. "GUID" (Globally Unique Identifier) is Microsoft's terminology commonly used in Windows registry keys, COM components, and C# / .NET development.
What is the collision probability of a UUID v4? ↓
With 122 bits of true cryptographic randomness, there are $2^{122}$ ($5.3 \times 10^{36}$) possible UUID v4 values. To have a 50% chance of generating a single duplicate, you would need to generate 1 billion UUIDs every second for roughly 85 years.
Why use UUID v7 instead of UUID v4 in SQL databases? ↓
When inserting random UUID v4 strings as primary keys into relational database tables (like PostgreSQL, MySQL InnoDB, or SQL Server), new records are inserted at random page locations in the index B-tree. This causes severe index page fragmentation and degrades insert performance as tables grow. UUID v7 solves this by sorting naturally by millisecond timestamp while retaining strong randomness.
Are generated UUIDs created locally or fetched from a server? ↓
All UUIDs are generated 100% locally in your browser using the native Web Crypto API (crypto.randomUUID() and crypto.getRandomValues()). Zero network calls are made, ensuring complete confidentiality.