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.
Distributed Systems
Each node independently generates UUIDs without centralized coordination. V1/V6/V7 support time sorting, convenient for sharding and archiving. V4 ensures no ID conflicts between different systems.
Session Management
Use V4 to generate unique session tokens. Use V7 combined with timestamps to implement automatic expiration mechanism. Use V5 to generate deterministic session identifiers from user IDs.
Best Practices
Version Selection Recommendations
- 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
Notes
- Generated IDs follow the UUID format and version rules (RFC 4122)
- Deterministic modes (V3/V5) generate the same UUID for the same inputs
- Generation and validation run locally in your browser
Privacy Note
- All generation and validation run locally; inputs are not uploaded
- The tool does not save your UUIDs or input data
