UUID Generator
Generate random v4 UUIDs. Supports bulk generation and multiple format options.
How to Use This Tool
- 1
Click the Generate button to create one or more random v4 UUIDs.
- 2
Use the Bulk field to specify how many UUIDs you need (up to 100 at once).
- 3
Choose your preferred format: standard hyphenated, uppercase, no hyphens, or wrapped in braces.
- 4
Click Copy All to copy the full list to your clipboard, or click a single UUID to copy it individually.
What is UUID?
A UUID (Universally Unique Identifier), also called a GUID (Globally Unique Identifier) in Microsoft contexts, is a 128-bit label standardised in RFC 4122. It is represented as 32 hexadecimal digits displayed in five groups separated by hyphens: 8-4-4-4-12 characters, for example 550e8400-e29b-41d4-a716-446655440000. The standard defines several versions; version 4 (the most common) is randomly generated with a few bits reserved to indicate the version and variant.
The appeal of UUIDs is that they can be generated independently by any system without coordination, yet the probability of two independently generated UUIDs colliding is astronomically small — roughly 1 in 5.3 × 10^36 for v4. This makes them ideal as primary keys in distributed databases, identifiers for objects in event-driven systems, filenames for user uploads, and anywhere you need a unique ID without a central authority handing them out.
UUID v4 versus alternatives: UUID v1 embeds the MAC address and timestamp, which leaks information about the generating machine and time. UUID v7 (a newer standard) encodes a millisecond timestamp at the start, making UUIDs sortable by creation time — useful for database index locality. UUID v4 is purely random, offering the best anonymity and the widest support across frameworks and databases.
Frequently Asked Questions
helpAre generated UUIDs truly unique?
They are unique for all practical purposes. A UUID v4 has 122 random bits, meaning you would need to generate approximately 2.7 × 10^18 UUIDs before the probability of a single collision reaches 50%. In practice, systems generate millions of UUIDs without collision.
helpWhat is the difference between UUID and GUID?
They are the same concept. GUID is Microsoft's term for the same 128-bit identifier format. The RFC 4122 standard uses UUID; Microsoft's documentation and COM/OLE systems use GUID. All modern GUIDs conform to the UUID standard.
helpShould I use UUID v4 or UUID v7 as a database primary key?
UUID v7 is generally better for database primary keys because it is time-ordered — new rows receive UUIDs that sort after older rows, preserving index locality and reducing B-tree page splits. UUID v4's random nature causes fragmentation in clustered indexes on large tables. That said, UUID v4 is sufficient for most use cases and has near-universal library support.
helpIs my data sent to a server?
No. UUIDs are generated locally in your browser using the Web Crypto API's crypto.randomUUID() or a polyfill based on crypto.getRandomValues(). Nothing is transmitted to any server.