UUID v1 is a time-based UUID version defined by RFC 4122. It encodes a 60-bit timestamp (100-nanosecond intervals since October 15, 1582), a 14-bit clock sequence, and a 48-bit node identifier (traditionally the MAC address of the generating machine). The version field (13th character) is always '1'.

How is UUID v1 different from UUID v4?

UUID v4 is randomly generated with 122 bits of randomness and contains no meaningful data. UUID v1 encodes the time of generation in its first three fields, making v1 UUIDs chronologically sortable and decodable. UUIDs generated close together in time will have similar prefixes in v1. UUID v4 is preferred when privacy matters since v1 can reveal when and from what machine it was generated.

Can I extract the timestamp from a UUID v1?

Yes. UUID v1 encodes the generation timestamp as a 60-bit value counting 100-nanosecond intervals since October 15, 1582 (the Gregorian calendar reform date). By reassembling the time_low, time_mid, and time_hi fields you can recover the original timestamp with sub-microsecond precision.

Is UUID v1 secure for use as a session token?

UUID v1 is NOT recommended as a session token or security credential. Because it encodes a timestamp and node identifier (potentially a MAC address), it is predictable — an attacker who knows one UUID v1 can narrow the search space for others generated around the same time. Use UUID v4 or a dedicated cryptographic token generator for security-sensitive identifiers.

Does this UUID v1 generator use my real MAC address?

No. Browsers do not expose MAC addresses for privacy and security reasons. This tool generates a random 48-bit node value (with the multicast bit set to 1 to signal it is not a real hardware address) using the Web Crypto API. The node is regenerated with each batch, so no identifying hardware information is ever used.

When should I use UUID v1?

UUID v1 is ideal for time-ordered logging and audit trails, append-heavy database writes (since sequential UUIDs reduce B-tree fragmentation), event sourcing systems, distributed tracing, and any use case where knowing the generation order of IDs is valuable. Apache Cassandra recommends UUID v1 for clustered time-series data. Avoid UUID v1 for anything requiring anonymity.

What is the structure of a UUID v1?

A UUID v1 has the format xxxxxxxx-xxxx-1xxx-yxxx-xxxxxxxxxxxx. The first three hyphen-delimited groups encode the timestamp (time_low 32 bits, time_mid 16 bits, time_hi 12 bits). The 13th character is always '1'. The fourth group encodes the clock sequence and variant. The last 12 hex digits encode the 48-bit node (typically a MAC address).

Free · Client-side · RFC 4122 · Time-Based

UUID v1 Generator

Generate time-based UUID v1 identifiers instantly. Encodes timestamp + node ID per RFC 4122 — entirely in your browser.

Part of WebEasier's UUID Generator suite — the most complete UUID toolkit on the web.

UUID v1 Generator

Timestamp + Random Node · crypto.getRandomValues()

All UUIDs generated locally in your browser. Node field uses a cryptographically random 48-bit value (not a real MAC address).

Quantity

Version

v1 (time-based)

Your UUID v1 values will appear here.
Set a quantity and click Generate.

What is a UUID v1?

A UUID v1 (version 1) is a time-based UUID defined by RFC 4122. It encodes the current timestamp as 100-nanosecond intervals since October 15, 1582, combined with a 14-bit clock sequence and a 48-bit node identifier (traditionally the machine's MAC address). The 13th character is always '1'.

6ba7b810-9dad-11d1-80b4-00c04fd430c8

Version Bit

13th char = '1'
xxxxxxxx-xxxx-1xxx-yxxx-…

Timestamp

60-bit
100ns intervals since
15 Oct 1582

Node Field

48-bit
MAC address or random (this tool uses random)

Standard

RFC 4122
IETF specification

Overview

What is a UUID v1?

UUID version 1 is the original time-based UUID format defined in RFC 4122. Unlike the random UUID v4, a v1 UUID contains meaningful information: the exact time it was created and the identity of the machine that created it.

This makes UUID v1 identifiers chronologically sortable — two UUIDs generated close together in time will have numerically adjacent timestamp fields — which is valuable for time-series databases and logging systems.

UUID v1 is widely used in Apache Cassandra, distributed event logs, and legacy enterprise systems. However, it is not recommended for use cases requiring anonymity, because the embedded timestamp and node reveal when and where the UUID was generated.

For general-purpose unique IDs with no timestamp exposure, consider our UUID v4 Generator.

UUID v1 Format

6ba7b810-9dad-11d1-80b4-00c04fd430c8

6ba7b810 time_low
32 bits

9dad time_mid
16 bits

11d1 time_hi + v=1
16 bits

80b4 clock_seq
16 bits

00c04fd430c8 node (48-bit)
MAC / random

The 13th character is always 1 (version).
The 17th character encodes the RFC 4122 variant (8, 9, a, or b).

Privacy Note

Traditional UUID v1 embeds the machine's MAC address in the node field, potentially identifying the host. This tool generates a random 48-bit node (with multicast bit set) to preserve privacy, as recommended for browser-based generators.

Structure

UUID v1 Field Anatomy

Every UUID v1 is composed of five fields, each encoding specific information.

xxxxxxxx time_low

xxxx time_mid

1xxx time_hi + ver

yxxx clock_seq

xxxxxxxxxxxx node

Field	Bits	Description	Fixed value?
`time_low`	32	Low 32 bits of the 60-bit timestamp	No — changes per generation
`time_mid`	16	Bits 32–47 of the 60-bit timestamp	No — changes per generation
`time_hi_and_version`	16	Bits 48–59 of timestamp + version nibble `0001`	Version nibble always `1`
`clock_seq_and_reserved`	16	14-bit clock sequence + 2 variant bits (`10`) per RFC 4122	Variant bits always `10`
`node`	48	Machine MAC address (or randomly generated in browser)	Random per batch (this tool)

Decoded Timestamp of Last Generated UUID

Generate a UUID above to decode its timestamp →

Live Examples

Example UUID v1 Values Generated Now

Fresh UUID v1 examples generated client-side on page load. Click any to copy.

How It Works

How UUID v1 Generation Works

UUID v1 generation follows RFC 4122 §4.2. The algorithm captures the current time as a 60-bit integer counting 100-nanosecond intervals since October 15, 1582 (the Julian-to-Gregorian calendar changeover), then slots that timestamp into the three time fields.

Because JavaScript's Date.now() has only millisecond resolution, this tool adds a sub-millisecond counter to simulate the finer granularity required by the spec, preventing duplicate timestamps within the same millisecond.

Get current time in 100ns intervals since 15 Oct 1582
Split into time_low, time_mid, time_hi
Set bits 12–15 of time_hi to 0001 (version 1)
Generate cryptographically random 14-bit clock sequence
Set variant bits to 10 (RFC 4122)
Generate random 48-bit node (multicast bit set to 1)
Format as xxxxxxxx-xxxx-1xxx-yxxx-xxxxxxxxxxxx

When to Use UUID v1

UUID v1 is the preferred choice when time-ordering matters:

Audit logs & event sourcing Cassandra time-series keys Append-only B-tree writes Distributed tracing IDs Time-stamped records Sequential event queues Message broker IDs Monitoring systems Enterprise legacy systems Legal audit trails

When NOT to Use UUID v1

Do not use UUID v1 for session tokens, CSRF tokens, API keys, or any security credential. The predictable timestamp component reduces the search space, making brute-force attacks feasible. Use UUID v4 for security-sensitive identifiers.

Comparison

UUID v1 vs Other UUID Versions

Understand when to choose UUID v1 over other versions.

Version	Generation Method	Sortable?	Private?	Best For
v1	Timestamp + MAC/random node	By timestamp	No (reveals time)	Time-ordered logging, Cassandra
v2	DCE Security (POSIX UID/GID)	Partial	No	Legacy DCE systems
v3	MD5 hash of namespace+name	No	Deterministic	Name-based IDs (MD5)
v4	Fully random (122 bits)	No	Yes	General purpose — use our UUID v4 tool
v5	SHA-1 hash of namespace+name	No	Deterministic	Name-based IDs (SHA-1)
v6	Reordered timestamp (RFC 9562)	Lexicographically	No	Sortable replacement for v1
v7	Unix ms timestamp + random (RFC 9562)	Lexicographically	Partial	Modern database-friendly sortable IDs

For most new projects, UUID v7 is the recommended sortable alternative to v1. For random/anonymous IDs, choose UUID v4. See the complete UUID versions guide on our main UUID Generator page.

FAQ

Frequently Asked Questions

Everything you need to know about UUID v1 and this generator.

A UUID v1 is a time-based UUID version defined by RFC 4122. It encodes the current timestamp as 60-bit value in 100-nanosecond intervals since October 15, 1582, along with a 14-bit clock sequence and a 48-bit node identifier (typically the MAC address of the generating machine). The 13th character is always '1', indicating version 1.

UUID v4 is entirely random (122 bits of entropy) and reveals nothing about when or where it was created. UUID v1 encodes the exact generation timestamp and node identifier. This makes v1 UUIDs chronologically sortable but not private. Use v4 for security tokens; use v1 (or the improved v6/v7) for time-ordered records. See our UUID v4 Generator for a direct comparison.

Yes. Reassemble the three time fields: take time_hi (bits 0–11, masking off version), shift left by 48, OR in time_mid shifted by 32, OR in time_low. Subtract the Gregorian epoch offset (122,192,928,000,000,000 100ns intervals) to get Unix nanoseconds. This tool extracts and displays the timestamp of your last generated UUID automatically in the "UUID v1 Field Anatomy" section.

No. UUID v1 is NOT suitable as a session token, CSRF token, or API key. The timestamp component makes it partially predictable — knowing one UUID v1 narrows the search space for nearby ones. For security-sensitive identifiers, always use UUID v4 or a dedicated cryptographic random token generator.

No. Web browsers do not expose MAC addresses. This tool generates a cryptographically random 48-bit node value for every batch, with the multicast bit (bit 0 of the first octet) set to 1 to signal it is not a real hardware address — exactly as RFC 4122 recommends for environments without MAC access. No identifying information about your device is ever used.

UUID v1 is well-suited for time-ordered logging, audit trails, Apache Cassandra primary keys (where the TIMEUUID type is UUID v1), distributed tracing, and any scenario where knowing the generaion order of identifiers matters. Its sequential timestamp fields reduce index fragmentation in append-heavy B-tree databases.

For new projects requiring sortable time-based UUIDs, UUID v7 (RFC 9562) is the modern recommendation. It uses a Unix millisecond timestamp in the most-significant bits, making it lexicographically sortable (v1's timestamp bits are shuffled, making lexicographic sort incorrect). UUID v7 also pairs better with modern databases. UUID v1 remains the right choice for legacy systems, Cassandra TIMEUUID compatibility, and exact RFC 4122 compliance.

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UUID v1 Generator

UUID v1 Generator

What is a UUID v1?

UUID v1 Format

UUID v1 Field Anatomy

Example UUID v1 Values Generated Now

How UUID v1 Generation Works

When to Use UUID v1

UUID v1 vs Other UUID Versions

Frequently Asked Questions

What is a UUID v1?

How is UUID v1 different from UUID v4?

Can I extract the timestamp from a UUID v1?

Is UUID v1 secure for session tokens?

Does this tool use my real MAC address?

When should I use UUID v1?

Should I use UUID v1 or UUID v7 for new projects?

Complete UUID Tools Directory

UUID Generation

UUID Validation

UUID Parsing

UUID Formatting

UUID Conversion

Developer UUID Generators

Alternative ID Generators

25+ UUID & ID Tools

Explore All Free Developer Tools