UUID Version Identifier
Identify the version and variant of any UUID. Supports versions 1-8, Nil, and Max UUIDs with detailed information.
Input
Output
Result
No value
Readme
What is a UUID version?
A UUID (Universally Unique Identifier) is a 128-bit identifier standardized by RFC 4122 and RFC 9562. Every UUID contains a version field that indicates how it was generated. The version is encoded in the 13th hexadecimal digit (the high nibble of the 7th byte), and it determines the algorithm and data sources used to create the identifier.
There are currently eight defined versions (v1 through v8), plus two special forms: the Nil UUID (all zeros) and the Max UUID (all ones). Each version serves a different purpose — some embed timestamps for chronological sorting, some use cryptographic hashes for deterministic generation, and others rely on random numbers for simplicity. Knowing the version helps you understand the properties, security implications, and intended use case of a UUID.
The variant field, encoded separately, identifies which UUID specification the identifier conforms to. Most modern UUIDs use the RFC 4122/RFC 9562 variant, but older systems may produce NCS or Microsoft variants.
Tool description
This tool takes any UUID as input and identifies its version number, version name, variant, generation method, and a detailed description of how that version works. It supports all standard versions (v1 through v8), as well as Nil and Max UUIDs. Simply paste a UUID and instantly see its full breakdown.
Examples
| Input UUID | Version | Name |
|---|---|---|
550e8400-e29b-41d4-a716-446655440000 |
4 | Random (v4) |
6ba7b810-9dad-11d1-80b4-00c04fd430c8 |
1 | Time-based (v1) |
018f3e88-5c00-7b3a-8512-2d4a3f8e9c01 |
7 | Unix Epoch Time-based (v7) |
00000000-0000-0000-0000-000000000000 |
Nil | Nil UUID |
ffffffff-ffff-ffff-ffff-ffffffffffff |
Max | Max UUID |
Features
- Detects all UUID versions from v1 to v8, plus Nil and Max UUIDs
- Identifies the variant (RFC 4122/9562, NCS, Microsoft, or Reserved)
- Shows a human-readable description explaining how the version is generated
- Displays the generation method used to produce the UUID
- Instant real-time identification as you type or paste
Use cases
- Debugging distributed systems: Determine whether UUIDs in your logs are time-based (v1/v6/v7) or random (v4) to understand if they carry embedded timestamps you can extract.
- Database optimization: Identify whether your primary keys use a sortable UUID version (v6, v7) or a random one (v4) that may cause index fragmentation.
- Security auditing: Detect v1 UUIDs that may leak MAC addresses or timestamps, helping you assess information disclosure risks.
How it works
The tool parses the UUID's hexadecimal structure to extract two key fields:
- Version: Read from the 13th hex digit (index 12 in the stripped hex string). This nibble directly encodes the version number (1–8). Nil and Max UUIDs are detected by checking whether all bits are zero or all bits are one.
- Variant: Determined by the most significant bits of the 17th hex digit (index 16). The bit pattern maps to one of four variant families: NCS, RFC 4122/9562, Microsoft, or Reserved.
UUID versions at a glance
| Version | Name | Key property |
|---|---|---|
| v1 | Time-based | Timestamp + MAC address |
| v2 | DCE Security | Timestamp + MAC + POSIX UID/GID |
| v3 | Name-based (MD5) | Deterministic from namespace + name |
| v4 | Random | 122 random bits |
| v5 | Name-based (SHA-1) | Deterministic, stronger hash than v3 |
| v6 | Reordered Time-based | Sortable variant of v1 |
| v7 | Unix Epoch Time-based | Unix ms timestamp + random, ideal for DB keys |
| v8 | Custom | Vendor-specific or experimental |
| Nil | Nil UUID | All 128 bits set to zero |
| Max | Max UUID | All 128 bits set to one |
FAQ
What is the difference between UUID version and variant? The version indicates the generation algorithm (time-based, random, hash-based, etc.), while the variant identifies which specification the UUID conforms to (RFC 4122, NCS, Microsoft). Most UUIDs you encounter will be RFC 4122/9562 variant.
Which UUID version should I use? For most applications, v4 (random) is the simplest and most widely supported. If you need time-sortable identifiers for database primary keys, v7 is the modern recommendation. Use v5 when you need deterministic UUIDs derived from a name.
Can this tool extract the timestamp from a UUID? This tool identifies the version and variant only. To extract embedded timestamps from v1, v6, or v7 UUIDs, use the dedicated UUID Time Extractor tool.