A UUID (Universally Unique Identifier), also called a GUID, is a 128-bit value written as 32 hexadecimal digits in five groups, like 550e8400-e29b-41d4-a716-446655440000. It is used as an identifier that can be generated independently anywhere with a negligible chance of collision.

What is the difference between UUID v4 and v7?

v4 is fully random — great for unguessable IDs but unordered, which can fragment database indexes. v7 embeds a millisecond Unix timestamp in its high bits, so v7 UUIDs sort chronologically and are far friendlier as primary keys while remaining practically unique.

Are these UUIDs generated securely?

Yes. They use the browser's crypto.randomUUID where available and otherwise crypto.getRandomValues, both cryptographically secure. Generation is entirely local — no UUID is sent to or logged by a server.

How unique are they really?

A v4 UUID has 122 random bits. You would need to generate about 2.7 quintillion of them before the chance of a single collision reaches even 50%, so for practical purposes they are unique without any central coordinator.

UUID Generator (v4 & v7, Bulk) — Local

On this page

How to use it
What a UUID is
v4 vs v7 vs NIL
How unique are they?
Why generate them locally
FAQ

How to generate UUIDs

Choose a version — v4 for fully random, v7 for time-ordered, or NIL for the all-zero placeholder — set how many you need (up to 1000), and press Generate. The results appear one per line, ready to copy or download as a .txt file. The formatting toggles let you match whatever your system expects: UPPER for uppercase hex, No hyphens for the compact 32-character form, and {braces} for the Microsoft-style registry/GUID format. Combine them freely.

What is a UUID?

A UUID — Universally Unique Identifier, called a GUID in Microsoft's world — is a 128-bit number written as 32 hexadecimal digits in the familiar 8-4-4-4-12 grouping, such as 550e8400-e29b-41d4-a716-446655440000. Its purpose is to let any machine mint an identifier independently, with no central authority and no coordination, while keeping the odds of two systems ever producing the same value vanishingly small. That makes UUIDs the default choice for primary keys, request and trace IDs, idempotency keys, file names and anywhere a globally unique handle is needed without a database round-trip to allocate it.

v4, v7 and NIL — which to use

Version 4 is the one most people mean by "a UUID": 122 of its 128 bits are random (the rest fix the version and variant). It is unpredictable and trivial to generate, which makes it ideal where the ID should reveal nothing and need not be ordered. Its one drawback shows up at database scale — because v4 values are random, inserting them as a clustered primary key scatters writes across the index and can hurt performance.

Version 7 is the modern answer to that. It places a 48-bit millisecond Unix timestamp in the high bits and fills the rest with randomness, so v7 UUIDs are time-sortable: generated-in-order means stored-in-order, which keeps database indexes tight while staying practically unique and still hard to guess. If you are choosing a UUID for a new primary key today, v7 is usually the better default. The NIL UUID is simply all zeros — a standard "no value" sentinel, useful as a placeholder or default.

Just how unique are they?

With 122 random bits, a v4 UUID has about 5.3×10³⁶ possible values. By the birthday-paradox maths, you would need to generate roughly 2.7 quintillion UUIDs before the probability of even one collision reached 50%. In everyday terms that means you can treat them as unique without a second thought — no coordination, no central registry, no checking. v7 keeps essentially the same uniqueness guarantee while adding useful ordering.

Why generate UUIDs locally

UUIDs are not secret, but a local generator is still the obvious choice: it is instant, works offline, and produces cryptographically strong randomness using the browser's own crypto API rather than a weak Math.random source. There is no reason to round-trip to a server — or to ask an AI model, which cannot produce genuinely random, correctly-versioned UUIDs reliably. gitime.dev generates them deterministically-formatted and securely-random in your tab, in bulk if you need thousands, with nothing uploaded or logged.

v4 & v7 plus the NIL UUID, all RFC-compliant.
Bulk generation up to 1000 at once.
Formatting toggles: uppercase, no-hyphen, braces.
Secure randomness via crypto.randomUUID/getRandomValues.
Local — nothing uploaded, works offline.

Frequently asked questions

What is a UUID?: A 128-bit universally unique identifier written as 32 hex digits in an 8-4-4-4-12 pattern, generated without any central authority.
v4 vs v7?: v4 is fully random and unordered; v7 embeds a millisecond timestamp so the IDs sort chronologically — better for database keys.
Are these generated securely?: Yes — via crypto.randomUUID or crypto.getRandomValues, locally; no UUID is uploaded or logged.
How unique are they?: A v4 has 122 random bits; you would need ~2.7 quintillion before a 50% collision chance — effectively unique.

UUID Generator