How are the UUIDs generated?

Each one comes from your browser's native crypto.randomUUID(), which draws from the platform cryptographically secure random source. That is a genuine CSPRNG, not Math.random(), so the output is suitable for database keys, session identifiers and distributed IDs where collisions and predictability actually matter.

How many UUIDs can I generate at once?

Between 1 and 100. Set the count in the number field and press Generate; each UUID gets its own row with an individual copy button, so you can lift a single identifier without grabbing the rest. Requesting a new batch replaces the previous batch entirely.

What makes a UUID a version 4?

A UUID is 32 hexadecimal characters in an 8-4-4-4-12 layout, and version 4 means the identifier is randomly generated rather than derived from a timestamp or a machine address. The 13th hex digit is always 4 to mark the version, and the first hex digit of the fourth group is one of 8, 9, a or b to mark the RFC 4122 variant. A UUID that encodes your MAC address and clock time is a version 1, and it leaks information about you — which is why version 4 is the right default here.

UUID v4 Generator

Free online uuid v4 generator for developers. Generate random UUID v4 identifiers. Fast and private.

Count:

bf14a708-7a1a-4c59-b9ff-611ac779f222

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Frequently Asked Questions about UUID v4 Generator

UUID v4 Generator — Random Unique Identifiers

This UUID v4 generator produces version 4 UUIDs — the 128-bit random identifiers used as database primary keys, file names, tracking parameters and distributed-system IDs. You can generate up to 100 at once, and each has its own copy button.

Generation uses crypto.randomUUID(), the browser's built-in Web Crypto function, which draws from a cryptographically secure source. That matters: identifiers generated with Math.random() are predictable, and predictable IDs are exploitable.

The Format, and What Each Part Means

A UUID looks like this:

550e8400-e29b-41d4-a716-446655440000

The 36-character display includes hyphens at fixed positions — 8-4-4-4-12 — and is a rendering convention. The value itself is 32 hex digits, or 128 bits. The layout is inherited from earlier UUID versions, and in a v4 most of the fields are not separate data at all:

Field	Bits	Meaning in a v4
time_low	32	Random.
time_mid	16	Random.
time_hi_and_version	16	High nibble is fixed at `4` to mark version 4. The rest is random.
clock_seq	16	High bits reserved for the variant (`10`), remainder random.
node	48	Random. In v1 this held the network MAC address, which is a privacy leak — one of the reasons v4 replaced it.

So a v4 UUID carries 122 bits of randomness, with 6 bits reserved for the version and variant markers. The 4 you see as the first character of the third group, and the a, b, 8 or 9 as the first character of the fourth group, are not random — they are fixed. That is a quick way to tell a v4 from a v1 by eye.

Why Random UUIDs Instead of Auto-Increment IDs

No coordination needed. Any node can mint an ID independently, so you can write to a database from several services without a shared counter and without collisions.
They do not leak volume. A sequential integer tells anyone who can read a URL exactly how many customers you have. A random ID reveals nothing.
Merging is painless. When two databases are combined, sequential IDs collide catastrophically. Random IDs do not.
They can be generated client-side. The browser can create the ID before the record is ever sent, which keeps ID logic out of the database layer.

The real cost is size: a UUID is 36 characters, so as a primary key it bloats every index that includes it. For a high-volume table, sequential integers or a compact identifier like a v7 UUID are often the better engineering choice. UUIDs are the right default for distributed, public or merge-prone cases.

Which UUID Version Do You Need?

Version	How it is built	Best for
v1	Timestamp + MAC address	Legacy systems. Avoid in new work — it leaks hardware identity.
v3	MD5 hash of a name	Deterministic IDs — the same input always yields the same UUID.
v4	Random	The safe general-purpose default. What this tool produces.
v5	SHA-1 hash of a name	Same as v3 but with a stronger hash.
v7	Timestamp prefix + random	Database keys — sortable by creation time, which v4 is not.

Related Identifier Tools

Bulk UUID Generator — CSV-ready output for seeding a database.
UUID Decoder — inspect any UUID and see its version, variant and embedded timestamp where one exists.
UUID v7 Generator — time-ordered identifiers for keys and log entries.
UUID v1 Generator — for working with older systems that still expect them.
Random Token Generator — shorter, URL-friendly secrets where a UUID's 36 characters are unnecessary.
Random Number Generator — sampling and testing rather than identifiers.

All generation happens locally in your browser, so these IDs are never seen by a server before you choose to use them.