UUID Generator
Generate random universally unique identifiers (UUIDs / GUIDs) instantly. Create version 4 (random) or version 7 (time-ordered) UUIDs in bulk, with formatting options — all generated locally in your browser.
82ce8d0f-1234-436b-ad54-e40ff14578ef08c9c465-6950-4431-8930-468b63ad1d369d0fb21f-7759-4b16-ade1-84ad4e67b4009e16e486-d078-46a8-bb46-604515ba7ef23825b1fa-7064-4ba7-a50f-4bd036104223Inspect a UUID
About the UUID Generator
A UUID (Universally Unique Identifier), also called a GUID, is a 128-bit value used to label data without a central authority — database keys, request IDs, file names. Version 4 UUIDs are fully random, so collisions are astronomically unlikely; version 7 embeds a timestamp so the IDs sort chronologically, which is friendlier to database indexes.
These identifiers are generated in your browser using a cryptographically secure random source, so they never touch a server. Bulk generation and formatting options make it easy to seed test data or grab a single ID for a quick task.
The UUID standard defines several versions beyond v4 and v7. Version 1 embeds a timestamp and the generating computer’s MAC address — useful for ordering, but it leaks machine identity, which is why it fell out of favor for anything public-facing. Versions 3 and 5 are deterministic: they hash a namespace plus a name (MD5 for v3, SHA-1 for v5), so the same input always produces the same UUID — handy for generating a stable ID from, say, a URL or an email address, rather than a random one. Version 4 became the default because it needs no coordination and reveals nothing about its origin.
Version 7 (formalized in RFC 9562, which supersedes the original RFC 4122) exists to fix a real operational problem: fully random v4 keys scatter writes across a database index in random order, which hurts insert performance and index locality at scale on B-tree-based primary keys. By putting a millisecond Unix timestamp in the first 48 bits, v7 UUIDs sort chronologically like an auto-increment ID while keeping the rest random — the reason it’s increasingly the recommended choice for new primary keys and request/trace IDs.
How to use it
- 1Choose the UUID version — v4 (random) or v7 (time-ordered).
- 2Set how many you need and any formatting options.
- 3Copy a single UUID or the whole batch.
Features
- UUID v4 (random) and v7 (time-ordered, sortable)
- Generate many at once
- Uppercase, braces and hyphen-free formatting
- Cryptographically secure randomness
- One-click copy of one or all
- Paste any UUID into the inspector to decode its version, variant, and (for v7) embedded timestamp
Frequently asked questions
What is a UUID?
A UUID (Universally Unique Identifier / GUID) is a 128-bit identifier, usually shown as 32 hex digits in five hyphen-separated groups, designed to be unique without coordination between systems.
What is the difference between UUID v4 and v7?
v4 is fully random. v7 is time-ordered — it begins with a Unix millisecond timestamp, so v7 UUIDs sort chronologically, which is better for database primary keys.
Are these UUIDs unique?
In practice, yes. v4 has 122 random bits, so the chance of a collision is negligible, and they are generated with a cryptographically secure random source.
Are the UUIDs generated privately?
Yes. Generation happens entirely in your browser; nothing is sent to a server.
What do UUID versions 1, 3 and 5 do?
v1 combines a timestamp with the generating machine’s MAC address (rarely used now since it leaks machine identity). v3 and v5 are deterministic — they hash a namespace and a name (MD5 for v3, SHA-1 for v5) so the same input always yields the same UUID, which is useful when you need a repeatable ID rather than a random one.
Why do v7 UUIDs make better database primary keys than v4?
A fully random v4 key inserts at a random position in a B-tree index every time, which hurts write locality and index performance at scale. v7 starts with a millisecond timestamp, so new rows insert in roughly chronological order — similar to an auto-increment ID — while still being globally unique and unguessable.
Is a UUID guaranteed to be unique?
Not mathematically guaranteed, but the collision probability is negligible in any realistic scenario — a v4 UUID has 122 random bits, so you would need to generate on the order of a billion UUIDs per second for roughly a hundred years before a 50% chance of one collision.
What is a nil UUID?
The nil UUID (00000000-0000-0000-0000-000000000000) is a reserved, all-zero value defined by the spec to explicitly represent "no UUID" — it is never produced by a generator, only used as a deliberate placeholder.