UUID / GUID Generator
Generate random cryptographically secure UUID version 4 strings in bulk. Copy single UUIDs or download a list instantly for database keys and testing.
Step-by-Step Instructions
Select UUID Version
Choose between UUID Version 4 (cryptographically secure random) or UUID Version 1 (timestamp + MAC address).
Specify Quantity & Format
Select number of UUIDs to generate (1 to 500) and choose uppercase vs lowercase formatting.
Configure Delimiters & Braces
Optionally include hyphens (standard 8-4-4-4-12 format), braces `{...}`, quotes, or comma-separated lists for SQL / JSON arrays.
Copy or Download UUIDs
Instantly copy generated UUIDs to clipboard or download as a plaintext file.
Key Features & Capabilities
- RFC 4122 compliant UUID v4 generator utilizing cryptographically secure `crypto.getRandomValues()` CSPRNG
- UUID v1 (timestamp-based), UUID v3/v5 (namespace MD5/SHA-1), and modern UUID v7 (Unix millisecond timestamp-ordered) engines
- Bulk generation up to 500 unique GUIDs / UUIDs with custom delimiters and casing
- GUID format compatibility for Microsoft .NET, SQL Server `uniqueidentifier`, and PostgreSQL `uuid` types
Frequently Asked Questions
What is a UUID / GUID and what does its structure represent?
A Universally Unique Identifier (UUID), or Globally Unique Identifier (GUID), is a 128-bit label standardized by RFC 4122. Represented as 32 hexadecimal digits separated by hyphens in five groups: `8-4-4-4-12` (e.g., `123e4567-e89b-12d3-a456-426614174000`), providing $2^{128} \approx 3.4 \times 10^{38}$ possible unique identifiers.
What is the difference between UUID Version 4 and UUID Version 7?
**UUID v4** is generated using pure cryptographically secure random bits, providing maximum unpredictability. **UUID v7** (RFC 9562) is timestamp-ordered, embedding a 48-bit Unix millisecond timestamp at the beginning followed by random bits. UUID v7 is vastly superior for database primary keys because sequential ordering prevents B-tree index fragmentation and improves database insert performance.
What is the probability of a UUID v4 collision?
The probability of a UUID v4 collision is practically zero. To have a 50% probability of generating just one collision, you would need to generate **1 billion UUIDs per second for roughly 85 years** (generating approximately $2.71 \times 10^{18}$ UUIDs).
How do UUID v4 and GUID differ in PostgreSQL vs SQL Server?
A UUID and GUID are structurally identical 128-bit integers. In PostgreSQL, they are stored using the native `UUID` datatype (stored efficiently as 16 raw bytes). In Microsoft SQL Server, they are stored as `UNIQUEIDENTIFIER` using a byte-ordering layout (endianness) where the first three components are stored in reverse byte order.
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