Need a full walkthrough of UUID versions, database patterns, and common mistakes? Read our UUID Generator guide — it pairs with this free UUID Generator tool and covers v1, v4, v7, nil, and GUID use cases.
What this tool does
A UUID (Universally Unique Identifier) is a 128-bit value written as 32 hexadecimal digits in five groups: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. Developers use UUIDs as database primary keys, correlation IDs in logs, opaque public URLs, and session tokens because they are designed to be unique without a central allocator.
Our generator runs entirely in your browser using crypto.getRandomValues() (and crypto.randomUUID() where supported). Nothing is sent to ShoutingNow servers.
UUID versions supported
| Tab | Standard | Best for |
|---|---|---|
| Version 1 | RFC 4122 — timestamp + random node | Legacy systems that expect time-ordered v1 IDs; generally prefer v7 for new work. |
| Version 4 | RFC 4122 — random | Default choice for primary keys, API IDs, and session tokens. |
| Version 7 | RFC 9562 — Unix ms + random | Sortable, time-ordered IDs for distributed databases (PostgreSQL, Cassandra). |
| Nil/Empty | RFC 4122 — all zeros | Placeholder meaning “no UUID assigned” — not a real identifier. |
| GUID | Same bits as UUID, braced uppercase | Windows, .NET, COM, and registry tooling that expects {XXXXXXXX-...}. |
How to generate UUIDs
- Pick a version tab — Version 4 is selected by default.
- Click Generate — a new UUID appears in the results panel with a one-click Copy button.
- Bulk mode — enter how many you need (1–500), click Generate, then Copy all or Download to a file.
- Switch versions — each tab keeps its own bulk count; results refresh when you generate again.
UUID format breakdown
Every standard UUID is 128 bits displayed as 36 characters including hyphens:
- 8 hex digits — time_low (v1/v7) or random (v4)
- 4 hex digits — time_mid or random
- 4 hex digits — version nibble + remaining bits
- 4 hex digits — variant field + clock/random
- 12 hex digits — node (v1) or random (v4/v7)
The version number appears in the third group (e.g. 4 for v4, 7 for v7). The variant bits in the fourth group mark the value as RFC-compliant.
Common UUID versions (reference)
| Version | Method | Notes |
|---|---|---|
| v1 | Timestamp + MAC/random node | Sortable by time; may leak hardware hints in older implementations. |
| v3 | Name-based (MD5) | Deterministic from namespace + name — not offered here; use when reproducibility is required. |
| v4 | Random | Recommended for most new applications. |
| v5 | Name-based (SHA-1) | Deterministic like v3 with stronger hash — generate in code when needed. |
| v7 | Unix timestamp + random | Modern time-sortable alternative to v1. |
Where UUIDs are used
- Database primary keys — avoid auto-increment collisions when merging shards.
- Public API resource IDs — opaque, non-sequential URLs.
- Order and transaction IDs — unique across services without coordination.
- Log correlation — trace a request across microservices.
- File and object storage keys — S3-style paths with no central counter.
Privacy and disclaimer
UUIDs from this tool are generated locally with your browser's secure random source. ShoutingNow does not store generated values. UUIDs are provided as-is without warranty of uniqueness — always enforce uniqueness constraints in your database. The nil UUID is a fixed constant, not a generated unique value.
Learn more
Read our step-by-step guide: UUID Generator Guide.