UUID v4 / v7 Generator — RFC 9562 Compliant
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How to Use
Select the UUID version (v4 or v7) and the number of UUIDs to generate, then click "Generate". UUIDs are automatically regenerated when you change any setting. Click a UUID to select and copy it, or use the copy button.
What Is UUID
UUID (Universally Unique Identifier) is a standard for generating unique identifiers in distributed systems. The format is "8-4-4-4-12" hexadecimal characters, totaling 36 characters (e.g., 550e8400-e29b-41d4-a716-446655440000).
UUID Versions
This tool supports UUID v4 and v7. There are several UUID versions, each with different generation strategies:
- v1: Based on timestamp and MAC address. Reveals when and where it was created.
- v4: Based on random numbers (122 bits of randomness). No information leakage. Most widely used.
- v5: Based on SHA-1 hash of a namespace and name. Deterministic — same input always produces the same UUID.
- v7: Based on Unix timestamp with random bits. Sortable by creation time. Newer standard (RFC 9562).
v4 uses crypto.randomUUID(). v7 uses crypto.getRandomValues() with an embedded timestamp. For most use cases (database keys, session IDs, API tokens), v4 is recommended. Use v7 when you need time-sortable IDs.
Privacy & Security
This tool uses the browser's built-in cryptographic APIs (crypto.randomUUID() for v4, crypto.getRandomValues() for v7). No data is ever sent to a server — all processing happens entirely in your browser.
FAQ
Should I use v4 or v7?
For most use cases, fully random v4 is the right choice. If you want IDs that sort by creation time or want to reduce index fragmentation — for example as database primary keys — v7 is better because it embeds a timestamp at the start.
Are the generated UUIDs sent to a server?
No. UUIDs are generated locally with the browser's built-in crypto APIs (crypto.randomUUID() for v4, crypto.getRandomValues() for v7) and are never transmitted or stored.
How many UUIDs can I generate at once?
You can generate up to 10 at a time. They regenerate automatically when you change a setting, and each one can be copied to the clipboard by clicking it or using the copy button.
Can the generated UUIDs ever collide?
v4 carries 122 bits of randomness, so collisions are effectively impossible in practice. v7 combines its timestamp with random bits, keeping IDs unique even when several are generated within the same millisecond.
Can someone read the creation time from a v7 UUID?
Yes — by design v7 embeds a Unix millisecond timestamp at the start, so the approximate creation time can be inferred. If you need to hide timing information, choose v4, which contains no time data.