What this tool does
UUID generation is a small task that interrupts flow more often than it should. This page gives you a fast way to create identifiers for tests, examples, mock payloads and local development work.
- Generates UUID v4 identifiers using the browser's cryptographically secure random number generator.
- Also generates ULID identifiers, which are sortable by time and useful for distributed systems where ordering matters.
- Lets you create a batch of unique identifiers at once so you can seed test fixtures, mock data or database records without repeating generation steps.
How to use it
- 1
Choose UUID v4 or ULID depending on which format your system expects.
- 2
Set the quantity if you need multiple identifiers at once.
- 3
Click Generate and copy the output into your fixture, test, migration or API payload.
- 4
Regenerate as many times as needed since each result is independent and unique.
Example
A developer needs ten unique IDs to seed a database migration fixture and generates them in a single step instead of running a script locally.
Format: UUID v4, Quantity: 1010 unique UUIDs ready to copy into a seed file or migration script.Use cases
- Creating IDs for fixtures, mocks and test payloads.
- Generating sample record identifiers for docs or demos.
- Producing quick placeholder values during local development.
Common mistakes
Reusing the same UUID in multiple records
UUID v4 values are meant to be used once per unique entity. Reusing the same ID across records defeats the purpose and causes uniqueness constraint violations.
Using UUID when ULID ordering is needed
UUID v4 is random and does not sort meaningfully by time. If your system benefits from lexicographic time ordering, use ULID instead.
Committing generated UUIDs as permanent test data without documentation
If a UUID is hardcoded in a fixture, document where it came from and what entity it represents so the next developer does not accidentally reuse it.
FAQ
What is the difference between UUID v4 and ULID?
UUID v4 is a randomly generated identifier with no time component. ULID encodes a millisecond timestamp in the first part, making it sortable and easier to debug in time-ordered systems.
Are these UUIDs safe for production use?
The browser's Web Crypto API provides a cryptographically secure random source, so the generated values are suitable for production uniqueness requirements.
Can I generate multiple UUIDs at once?
Yes. Set the desired quantity and copy the batch output into your fixture or seed file.
Does this tool store or log generated UUIDs?
No. Generation runs locally and values are not sent to any external service.
When should I prefer ULID over UUID?
Prefer ULID when you need identifiers that sort chronologically, such as for event logs, audit trails or append-only tables.
Privacy and security
- UUID generation runs locally in the browser.
- No generated values are requested from a third-party service.
- That keeps small utility tasks fast and self-contained.
Related tools
Related tools for the next step in the same workflow:
Next step
Generate the UUIDs you need, then move back into formatting or conversion tools to finish the surrounding task.