UUID v1 Generator

Every time your application needs to identify a record, resource, or event without asking a central server for the next available number, a UUID (Universally Unique Identifier) is the answer — and the UUID version 1 generator above lets you create one instantly. What makes UUID v1 distinctive is that each value encodes the precise moment it was created alongside the hardware address of the generating machine, giving you a timestamp-based UUID that carries its own chronological context.

UUID Structure: The 8-4-4-4-12 Format

A UUID is a 128-bit label — stored as 16 bytes — represented as 32 hexadecimal characters arranged in five groups separated by hyphens, the canonical 8-4-4-4-12 pattern:

xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx

A real example: 6ba7b810-9dad-11d1-80b4-00c04fd430c8. Here M is the version indicator (the digit "1" for a Version 1 UUID) and N encodes the variant bits. The structure is governed by RFC 4122 (2005) and its successor RFC 9562 (2024). To generate uuid v4 quickly and privately — no data ever leaves your browser — use the UUID v4 Generator.

Anatomy of a Version 1 UUID

A version 1 UUID packs three distinct components into its 128 bits. Using 6ba7b810-9dad-11d1-80b4-00c04fd430c8 as an example:

• Time-low field (6ba7b810): the least significant 32 bits of the 60-bit UTC time-value, measured in 100-nanosecond intervals since October 15, 1582
• Time-mid field (9dad): the next 16 bits of the same time-value
• Time-high-and-version field (11d1): the most significant 12 bits of the time-value, plus 4 version bits set to "0001" — the leading "1" confirms this is version 1
• Clock sequence (80b4): a counter incremented when the clock is set backwards or the node address changes, preventing duplicate output
• Node field (00c04fd430c8): the 48-bit hardware network interface address — the component that anchors uniqueness to a specific machine

Because the time-value sits at 100-nanosecond resolution, UUIDs created in sequence sort roughly into chronological order — a property a fully random UUID cannot offer.

How Unique Is a UUID v1?

Unlike UUID v4, which draws uniqueness from 122 random bits, a UUID v1's uniqueness comes from a different source: the current time-value combined with the host's node identifier. Because the time resolution is fine enough (100-nanosecond intervals) and the clock-sequence field guards against clock rollbacks, duplicates remain extraordinarily unlikely as long as clocks are properly managed — even across many machines generating values simultaneously. Retrieve the nil uuid for use as a default foreign key, null reference, or initial state in your schema.

When to Choose UUID v1 Over v4 or v7

UUID v1 in Databases

Every major storage system supports UUID natively or via extension:

• PostgreSQL — native uuid type; the uuid-ossp extension provides uuid_generate_v1()
• MySQL / MariaDB — store as CHAR(36) or BINARY(16); the built-in UUID() function produces v1-style values
• SQL Server — uniqueidentifier column type, via NEWID()
• Oracle — RAW(16) or VARCHAR2(36), via SYS_GUID()

UUID primary keys carry a real tradeoff: higher storage than integer keys and, for fully random v4 values, index fragmentation from arbitrary insert order. UUID v1 partially mitigates this — rows inserted close together share similar time prefixes, reducing fragmentation compared to purely random UUIDs, though UUID v7 improves on this further with a clean sequential prefix.

Debugging with UUID v1's Embedded Timestamp

Because each UUID v1 value embeds a time-value, you can decode the exact creation time from any UUID in your logs or event records — useful for trace correlation across systems without a separate timestamp column. Our UUID Decoder tool extracts it directly.

Frequently Asked Questions