A version-1 UUID encodes a 60-bit timestamp (100-nanosecond intervals since 1582) plus a clock sequence and a node identifier. Because the timestamp is embedded, v1 UUIDs are roughly ordered by creation time.

Does this expose my MAC address?

No. The classic v1 spec uses the network card's MAC for the node field, but browsers cannot read it. This tool generates a random node with the multicast bit set, so no hardware identity ever leaves your machine.

Is anything uploaded?

No — the timestamp, random node, and clock sequence are all computed in your browser and nothing is uploaded.

What is the difference between UUID v1 and UUID v4?

v1 is time-based: it embeds a timestamp, clock sequence and node, so the values are roughly ordered by creation time. v4 is almost entirely random with no time information. Use v1 when you want loose time-ordering, v4 when you want pure unpredictability.

How is the timestamp stored in a v1 UUID?

As a 60-bit count of 100-nanosecond intervals since 15 October 1582 (the start of the Gregorian calendar). It is split across the time-low, time-mid and time-high fields of the UUID.

What is the clock sequence for?

It is a value that changes if the system clock is set backwards or the node identifier changes, reducing the chance of duplicate UUIDs generated in the same instant. This tool sets it randomly per batch.

Should I use v1 or v7 for new projects?

For new time-sortable identifiers UUID v7 is usually preferred: it puts a plain Unix millisecond timestamp first, sorts naturally as a string, and carries no node field. v1 remains useful for compatibility with existing v1-based systems.

Where do I see the version and variant in the UUID?

The version digit is the first character of the third group (a 1 for v1), and the variant is encoded in the high bits of the first character of the fourth group (typically 8, 9, a or b).

What is the UUID v1 Generator?

Free UUID v1 generator — create time-based RFC 4122 version-1 UUIDs with a randomised node ID so your real MAC address never leaks. Runs entirely in your browser, nothing is uploaded. It runs free in your browser on Gera Tools, with nothing uploaded.

UUID v1 Generator — Gera Tools

Name: UUID v1 Generator
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

Time-based UUID v1 generator

A UUID v1 is a 128-bit identifier defined by RFC 4122 that is built from the time of creation rather than pure randomness. It combines a timestamp, a clock sequence and a node identifier, which means a series of v1 UUIDs is roughly ordered by when each was generated — useful for debugging, loosely time-sortable keys, or interoperating with systems that already use v1. This generator mints one or a batch in your browser.

How it works

The 128 bits are laid out as:

A 60-bit timestamp counting 100-nanosecond intervals since 15 October 1582, split across the time-low, time-mid and time-high fields.
A version nibble set to 1 and the RFC 4122 variant bits.
A clock sequence to guard against clock rollbacks.
A 48-bit node identifier.

The classic spec used the machine’s MAC address for the node, but browsers cannot read hardware addresses, so this tool generates a random node with the multicast bit set — guaranteeing a spec-compliant UUID while leaking no hardware identity. A batch shares one random node and clock sequence and advances the timestamp so the IDs stay roughly ordered.

Example

A generated v1 UUID looks like f47ac10b-58cc-11ee-8c99-0242ac120002. The 1 at the start of the third group (11ee) marks it as version 1, the first three groups encode the timestamp, the fourth group (8c99) holds the variant and clock sequence, and the final group (0242ac120002) is the random node.

Field	Bits	Source
Timestamp	60	100-ns intervals since 1582
Version	4	Fixed: 1
Clock sequence	14	Random per batch
Node	48	Random, multicast bit set

Everything runs entirely in your browser — the timestamp, random node and clock sequence are all computed locally, and nothing is uploaded.

When to reach for v1 over v4 or v7

UUID v1 has a narrower use case than v4 or v7, but it remains valuable in specific situations:

Interoperability with existing systems. Many older databases, libraries, and protocols were built around v1 UUIDs and expect the specific layout. Cassandra uses v1 as its native UUID type; some SMTP message IDs embed v1 UUIDs; certain distributed systems use v1 as a form of soft ordering for events. If you are interfacing with a system that generates or expects v1, this generator lets you produce compatible values without installing a native tool.

Rough time-ordering without coordination. Because the timestamp is embedded, a sequence of v1 UUIDs generated on the same machine tends to sort in creation order — useful for event logs where you want to visually scan a sequence and see an approximate time order without parsing dates separately.

Debugging and inspection. The timestamp in a v1 UUID is recoverable. Given a v1 UUID, you can extract the 60-bit count of 100-nanosecond intervals since 15 October 1582, convert it to a readable timestamp, and know approximately when it was created. This is sometimes useful in forensics or debugging sessions.

Why v1 is not ideal for most new systems

For new systems, the better choice is usually v7 (time-ordered, Unix millisecond prefix, sortable as a string) or v4 (fully random, no time information needed). The original v1 timestamp layout splits the high and low bytes of the timestamp in a non-intuitive order that does NOT sort naturally as a string — the most-significant time bits are in the middle of the string, not at the front. This means v1 UUIDs do not sort by creation time when compared as text or bytes, despite containing time information. v7 fixes this by placing the timestamp in the most significant bits.

Additionally, the classic v1 node field (typically the MAC address) poses a privacy concern in browser contexts — though this generator avoids the issue by using a random node with the multicast bit set.