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UUID Generator

Generate RFC 4122 compliant UUIDs (v4) in bulk. Everything runs locally in your browser.

UUID Version

Generated using random (or pseudo-random) numbers. Most commonly used.

Generated UUID

d88a946c-0ff0-4867-8b53-86042af8e686

UUID Anatomy

d88a946c-0ff0-4867-8b53-86042af8e686
d88a946c

Random

32 random bits

0ff0

Random

16 random bits

4867

Version + random

Version 4 + 12 random bits

8b53

Variant + random

RFC variant + 14 random bits

86042af8e686

Random

48 random bits

Bulk Generate

max 1000

About UUIDs

What is a UUID?

A Universally Unique Identifier (UUID) is a 128-bit value used to uniquely identify objects or entities on the internet. UUIDs are standardized by RFC 4122 and represented as 32 hexadecimal digits in the format xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx where M is the version and N is the variant.

Version 1

Generated using the current timestamp and the MAC address (or random node).

Version 3

Generated by hashing a namespace UUID and a name using MD5.

Version 4

Generated using random (or pseudo-random) numbers. Most commonly used.

Version 5

Generated by hashing a namespace UUID and a name using SHA-1.

All UUIDs are generated locally in your browser using the uuid library. Nothing is sent to any server.

What is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit value written as 32 hex digits in five dash-separated groups, e.g. 550e8400-e29b-41d4-a716-446655440000. The 13th hex digit encodes the version and the 17th encodes the variant — that is why every v4 UUID has a 4 in that position. Standardized by RFC 4122, UUIDs let independent machines mint identifiers without ever talking to a central authority, which is exactly what distributed systems need.

What is the difference between UUID v1, v3, v4, and v5?

Version 4 is pure randomness — 122 random bits — and is the right default for almost everything. Version 1 embeds a 60-bit timestamp plus a node identifier, so it sorts roughly by creation time but leaks when it was made. Versions 3 and 5 are deterministic: they hash a namespace UUID plus a name (MD5 for v3, SHA-1 for v5), so the same input always yields the same UUID — useful for stable IDs derived from URLs or hostnames. This tool generates all four.

Can two UUIDs collide?

In practice, no. A v4 UUID has 2^122 possible values; you would need to generate about 103 trillion UUIDs before the odds of a single collision reach one in a billion. The real-world collisions people do hit come from bugs, not math: seeding a non-cryptographic PRNG identically across servers, cloning a VM image that reuses entropy state, or copy-pasting an example UUID into production code. Use a proper generator and collisions are a non-issue.

What about UUID v7?

UUID v7, standardized in RFC 9562 (2024), puts a Unix millisecond timestamp in the high bits followed by random bits, so values sort by creation time. That ordering fixes the main complaint about v4 as a database key: random inserts scatter across a B-tree index and cause page splits. If you need time-ordered IDs today, v1 also embeds a timestamp (this tool generates it), though its byte layout does not sort lexically the way v7 does.

How do I generate a UUID on the Linux command line?

The util-linux package ships uuidgen: plain uuidgen or uuidgen -r emits a random v4, uuidgen -t a time-based v1, and uuidgen -s --namespace @dns -N example.com a v5. With no tools installed, cat /proc/sys/kernel/random/uuid works on any Linux kernel. In scripts, python3 -c 'import uuid; print(uuid.uuid4())' is portable, and PostgreSQL 13+ has gen_random_uuid() built in — no extension needed.

Are UUIDs good database primary keys?

They are popular for good reasons — no coordination, safe to generate client-side, no sequence bottleneck — but know the trade-offs. A UUID is 16 bytes versus 8 for a bigint, and every secondary index carries that cost too. Random v4 keys fragment clustered indexes (MySQL InnoDB suffers most), which is why time-ordered schemes like v7 or ULID exist. Also avoid using UUIDs as security tokens by themselves; uniqueness is not the same as authorization.

Is it safe to generate UUIDs in this browser tool?

Yes. UUIDs are produced locally by the uuid JavaScript library, which draws randomness from crypto.getRandomValues() — the same OS-level CSPRNG that openssl uses. No network request is made and nothing is logged or stored server-side, so generated IDs are safe to use for internal systems. Bulk mode creates up to 1000 UUIDs at once that you can copy or download as a .txt file, and the anatomy view breaks down what each segment of the UUID means.