About UUID version 4
Universally unique identifiers remove coordination overhead when databases need primary keys or when microservices must correlate events without a central allocator. Version 4 IDs are random (with reserved version and variant bits), making collisions astronomically unlikely for practical engineering purposes.
This generator prefers crypto.randomUUID() when the browser exposes it, falls back to getRandomValues, and only then uses a Math-based generator clearly labeled as non-cryptographic. You can emit up to one hundred IDs per batch and optionally uppercase them for systems that require uppercase hex.
When batch generation helps
- Seeding integration tests with deterministic-looking but unique identifiers.
- Provisioning temporary filenames for offline demos.
- Generating correlation IDs for log pipelines during load tests.
How to use this page
- Set the desired count (1–100).
- Toggle Uppercase if downstream systems require uppercase hex digits.
- Click Generate to populate the output pane.
- Copy the block into spreadsheets, fixtures, or shell scripts.
Privacy
IDs are created locally. They are not logged by this tool, although your browser extensions or analytics may still record page views normally.
Frequently asked questions
- Are these IDs cryptographically secure?
- When Web Crypto is available, yes for typical engineering threat models. Avoid the Math fallback for secrets.
- Can I generate ULIDs?
- Not on this page—UUID v4 only.
- Why limit batches to 100?
- It keeps the UI responsive and discourages accidental thousand-line pastes into editors.
- Do UUIDs leak entropy?
- They reveal nothing beyond random bits; still, do not embed sequential business identifiers if those must stay private.