Davemi ToolsUUID Generator
Generate UUID v4 (random) or v7 (timestamp-sortable) in bulk. Cryptographically secure, instantly copyable, perfect for databases, APIs & testing.
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What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit identifier standardized by RFC 9562. Written as 32 hexadecimal digits in the form 8-4-4-4-12, UUIDs are designed to be globally unique without a central coordinating authority. They're used everywhere: database primary keys, API request IDs, distributed systems, session tokens, and more.
UUID v4 vs v7
| Feature | v4 | v7 |
|---|---|---|
| Source | 122 random bits | 48-bit timestamp + random |
| Sortable | No | Yes (by time) |
| DB indexing | Random I/O | Sequential appends |
| Best for | General purpose | Primary keys |
| RFC | RFC 9562 §5.4 | RFC 9562 §5.7 |
Common use cases
- Database primary keys (PostgreSQL, MySQL, MongoDB)
- Distributed system identifiers
- API request/response correlation IDs
- Session & authentication tokens
- File names for uploaded content
- Message queue deduplication keys
- Test data generation
UUID anatomy
█ time_low / random
█ time_mid / random
█ version nibble (4 = v4)
█ variant bits (8/9/a/b)
Frequently Asked Questions
What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit label used to uniquely identify information in computer systems. Written as 32 hex digits in 5 groups separated by dashes (e.g., 550e8400-e29b-41d4-a716-446655440000), UUIDs are designed to be unique across space and time without requiring a central authority.
What's the difference between UUID v4 and v7?
UUID v4 is purely random — all 122 bits (after version and variant) are random, making collisions astronomically unlikely. UUID v7 embeds a Unix millisecond timestamp in the first 48 bits followed by random data, making them naturally sortable by creation time — ideal for database primary keys where insert order matters.
Are these UUIDs truly random and unique?
Yes. This tool uses crypto.getRandomValues(), a cryptographically secure random number generator built into all modern browsers. With 122 random bits in a v4 UUID, you'd need to generate 2.7 quintillion UUIDs to have a 50% chance of a single collision.
Does this tool upload my UUIDs anywhere?
No. All UUID generation happens entirely in your browser using JavaScript. Nothing is sent to any server — the UUIDs are created on your device and only exist in your browser tab.
When should I use UUID v7 over v4?
Use UUID v7 when the IDs will be used as database primary keys (especially in B-tree indexes), when you need rough time-ordering of records, or when you want to extract a creation timestamp from the ID later. Use v4 when you need maximum randomness and don't care about ordering.
Can I use UUIDs as database primary keys?
Yes, and it's a common pattern. UUID v7 is particularly well-suited because its timestamp prefix makes new inserts append to the end of B-tree indexes, avoiding random I/O. UUID v4 works too but can cause index fragmentation in large tables due to its random nature.
How many UUIDs can I generate at once?
You can generate up to 1,000 UUIDs in a single batch. All generation happens instantly in your browser. You can copy them all at once or individually.
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