UUID Generator Tutorial
Detailed guide, best practices, and FAQ
Use Cases
The UUID/ULID generator is useful for database primary keys, distributed system IDs, test data seeding, and session tokens. Use it when you need globally unique identifiers without a centralized ID service, or time-ordered IDs for logs and event streams.
Features
- Three formats: UUID v4 (random), UUID v7 (time-ordered), ULID (26-char lexicographically sortable)
- Batch generation: up to 50 IDs at once
- Format control: toggle uppercase and hyphens
- Cryptographically secure: uses crypto.getRandomValues true random source
- Fully local: never uploaded, safe for production use
Examples
Example 1: Scenario 1: Need 100 primary keys for database test data? Slide count to 50, click Generate twice, copy all to your SQL file.
Example 2: Scenario 2: Debugging a distributed system needs sortable event IDs — pick UUID v7; sorting the strings gives time order.
Example 3: Scenario 3: Frontend needs a temporary session ID — pick ULID (shorter, URL-safe), disable hyphens to get a 26-char string.
Best Practices
- Prefer UUID v7 or ULID in production for time-ordered, index-friendly keys
- Use ULID for URL-friendly IDs (no hyphens, 26 chars, case-insensitive)
- Avoid UUID v4 as a database primary key (random order causes B-tree fragmentation)
- For security-sensitive tokens, use this tool's crypto.getRandomValues, never Math.random
FAQ
What is the difference between UUID v4 and v7?
v4 is fully random with no ordering. v7 embeds a 48-bit millisecond timestamp in the first bits, so string sorting equals time sorting — ideal for database indexes.
Why is ULID better than UUID?
ULID is 26 chars of Crockford Base32 — 10 chars shorter than UUID (36 chars), case-insensitive, lexicographically sortable by time, and URL-safe with no special characters.
Are the generated IDs cryptographically secure?
Yes. This tool uses the Web Crypto API's crypto.getRandomValues, the same cryptographically secure source behind crypto.randomUUID.
Can I generate multiple IDs at once?
Yes. Drag the Count slider up to 50. After generation, click "Copy All" to copy them all to the clipboard.