UUID Generator

Introduction

UUID generator supports creating multiple versions of Universally Unique Identifiers (UUID), including time-based, random, hash-based, and special value UUIDs. Also provides UUID checker functionality for validating and analyzing version, variant, and validity of existing UUIDs. Suitable for database primary key generation, distributed system identification, session management, and other scenarios.

Core Features

UUID Generation

Multi-version Support: Generate V1, V3, V4, V5, V6, V7 version UUIDs
Special Values: Create NIL (all zeros) and MAX (all ones) UUIDs
Batch Generation: Generate up to 100 UUIDs at once
Namespace Support: V3 and V5 support custom namespace and name

UUID Checker

Validity Verification: Check if string conforms to UUID format
Version Detection: Automatically recognize UUID version (1-7)
Variant Analysis: Determine UUID variant (RFC 4122, NCS, Microsoft, Future)
Special Detection: Identify NIL and MAX UUIDs
Normalization: Display lowercase standard format UUID

UUID Version Details

NIL UUID

Format: 00000000-0000-0000-0000-000000000000

Special UUID with all bits set to zero, used for:

Null value placeholder in databases
Default value for uninitialized states
Identifier for missing or invalid IDs

MAX UUID

Format: ffffffff-ffff-ffff-ffff-ffffffffffff

Special UUID with all bits set to one, used for:

Maximum value sentinel for boundary testing
Upper limit for range queries
Special marker value

V1: Time-based

Uses current timestamp and MAC address for generation, characteristics:

Time-ordered: Natural sorting by generation time
Uniqueness: Combined with timestamp and hardware address, extremely low collision probability
Privacy Concerns: May expose MAC address and generation time
Use Cases: Log recording, event tracking (note privacy)

V3: MD5 Hash

Generated through MD5 hash of namespace UUID and name, characteristics:

Deterministic: Same input always produces same UUID
Namespace Isolation: Same name in different namespaces produces different UUIDs
Compatibility: Uses MD5 algorithm, fast computation
Use Cases: Need to generate consistent identifier from name (legacy systems)

V4: Random

Uses random or pseudo-random numbers for generation, characteristics:

Simplicity: Easiest to implement, no additional parameters needed
Privacy: Does not contain time or hardware information
High Collision Rate: Theoretically collisions exist but probability extremely low (1 in 2^122)
Use Cases: General unique identification, most commonly used version

V5: SHA-1 Hash

Similar to V3 but uses SHA-1 hash, characteristics:

Deterministic: Same input always produces same UUID
Stronger Security: SHA-1 has better collision resistance than MD5
Recommended Alternative: New applications should prioritize V5 over V3
Use Cases: Need to generate consistent identifier from name

V6: Reordered Time-based

Improved version of V1, rearranging timestamp fields, characteristics:

Time-ordered: Maintains time sorting characteristics
Database Friendly: More suitable for B-tree indexes and sorting
Compatibility: Uses same time precision as V1
Use Cases: Database primary keys, distributed IDs requiring time ordering

V7: Unix Timestamp

Uses millisecond Unix timestamp and random bits, characteristics:

Time-ordered: Natural sorting by generation time
Privacy: Does not contain MAC address
Database Friendly: Suitable as primary key, high index efficiency
Recommended Use: Modern choice combining time ordering and privacy

How to Use

Generate UUID

Select Version: Choose UUID version from selector (NIL, MAX, V1-V7)
Configure Options (applies to V3/V5):
- Select predefined namespace (DNS, URL, OID, X500)
- Or enter custom namespace UUID
- Enter name to hash
Set Quantity: Choose number of UUIDs to generate (1-100)
View Results: Generated UUIDs display in right panel
Copy Usage: Click individual UUID to copy, or use "Copy All" button

Check UUID

Paste UUID: Enter UUID string in checker input box
View Analysis:
- Validity status (valid / invalid)
- Normalized form (lowercase standard format)
- Version number (1-7 or unknown)
- Variant type (RFC 4122, NCS, Microsoft, Future)
- Special type detection (NIL / MAX)
Verify Results: Confirm UUID conforms to expected format and version

Use Cases

Database Primary Keys

Use V4 to generate random primary keys, avoiding sequence number data volume leaks. Use V7 to generate time-ordered primary keys, improving insert performance and range query efficiency. Use V5 to generate deterministic primary keys from business identifiers.

General Scenarios: Use V4 (random) or V7 (time-ordered)
Database Primary Keys: Prioritize V7, then V4
Deterministic Generation: Use V5 (recommended) or V3 (compatibility)
Hide Hardware Info: Avoid V1, choose V4 or V7
Time Ordering: Use V1, V6, or V7