UUID Generator

What it does

The UUID Generator creates universally unique identifiers — also called GUIDs — in every common version: random v4, time-ordered v7, classic timestamp v1, reordered-time v6, name-based v3 (MD5) and v5 (SHA-1), custom v8, plus the special nil (all zeros) and max (all ones) values. Generate one UUID or a batch of up to 1,000, uppercase or lowercase, with or without hyphens, and reproduce the exact same list later by reusing a seed.

Which UUID version should I use?

• v4 (random) — the default almost everywhere: 122 random bits, no embedded information. Use it when you just need a unique ID.
• v7 (time-ordered) — starts with a Unix timestamp, so values sort by creation time. The best choice for database primary keys, where random v4 keys fragment indexes.
• v1 / v6 — older timestamp formats; v6 is v1 with the time bits reordered to be sortable. Mostly useful for compatibility with existing systems.
• v3 / v5 (name-based) — deterministic: hashing the same namespace and name always yields the same UUID. Use them to derive stable IDs from existing keys like domain names or URLs.
• nil / max — the special all-zero and all-one UUIDs, handy as sentinels and edge-case fixtures in tests.

Common use cases

• Primary keys and object IDs in test fixtures and database seeds.
• Placeholder IDs while designing APIs, schemas, and mock responses.
• Bulk ID lists for load tests, CSV imports, and demo datasets.
• Stable, derived identifiers via v3/v5 (same input → same UUID).

Settings

• Version — any of v1, v3, v4, v5, v6, v7, v8, nil, or max.
• Namespace / Name — used by the name-based versions (v3 and v5); pick a standard namespace such as DNS and enter the name to hash.
• How many — generate 1 to 1,000 UUIDs at once.
• Uppercase — output 550E8400-… instead of 550e8400-….
• Hyphens — toggle the standard 8-4-4-4-12 grouping.
• Seed — the same seed and settings always regenerate the same list.

Privacy note

Everything runs locally in your browser — UUIDs are never uploaded, logged, or sent to a server. Values generated here are synthetic fixtures for development and testing.

FAQ

Is a UUID the same as a GUID? Yes — GUID is Microsoft’s name for the same 128-bit identifier format. The strings are interchangeable.

Can I reproduce the same UUIDs later? Yes. This is a seeded generator: the same seed, version, and count always produce the identical list — useful for repeatable tests and golden files.

Are these UUIDs secure or guaranteed unique? No. Seeded output is deterministic, so don’t use it for session tokens, API keys, or anything security-sensitive — use the Secure Token Generator instead. For production IDs, use your language’s crypto-backed UUID library.

What’s the difference between UUID v4 and v7? v4 is fully random; v7 embeds a millisecond timestamp in the leading bits so IDs sort chronologically. If they’re database keys, v7 usually performs better.