How to generate
Use the ready-made UUID, or choose a quantity and format, then select Generate another. Copy individual rows, copy the exact visible batch, or export TXT, CSV, or JSON.
UUID v1 Generator
Generation settings
One UUID is ready.
Copy All and Download TXT exactly match the visible output.
Advanced options
Added to each formatted value.
Added to each formatted value.
Random bytes come from Web Crypto; the multicast bit marks a non-IEEE node.
Enter exactly 12 hexadecimal digits. A custom value may identify hardware.
Field labels (color is supplementary):
- time_low
- time_mid
- version + time_hi
- variant + clock sequence
- node
Running local compliance checks…
Generated UUIDs
TXT matches the output above. CSV is a uuid column; JSON is a valid string array. Press Ctrl/Cmd + Enter to regenerate.
Advertisement
UUID v1 Inspector
The first generated UUID is decoded automatically, or paste a canonical, braced, compact, or URN value.
Inspection happens locally.
Worked UUID v1 example
f81d4fae-7dec-11d0-a765-00a0c91e6bf6 follows the 8-4-4-4-12 layout:
f81d4faeis time_low;7decis time_mid.11d0is time_hi_and_version. Its first hex digit is1, identifying version 1.a765contains the variant and clock sequence. A first digit of8,9,a, orbmeans the RFC variant; after removing those two variant bits, the clock sequence is10085.00a0c91e6bf6is the 48-bit node value.
The fields reassemble to Gregorian ticks 0x1d07decf81d4fae, which decodes to 1997-02-03T17:43:12.2168750Z. To create this value from Unix time: Gregorian ticks = Unix milliseconds × 10,000 + 122,192,928,000,000,000.
How and when to use UUID v1
When to use v1
Use v1 for legacy compatibility or a system that specifically requires its timestamp, clock-sequence, and node layout. Use v7 for new time-ordered database keys and v4 for opaque general-purpose identifiers.
Ordering and security limits
V1 embeds a 60-bit Gregorian-epoch timestamp, but its timestamp fields are rearranged in the canonical string. It is not reliably lexicographically sortable across longer periods. UUIDs are identifiers—not secrets, passwords, or authentication tokens.
Privacy and generation method
This page runs locally. The browser Web Crypto API supplies the 14-bit clock sequence and random node. The node’s multicast bit is set, and generated values are never submitted to Starlight Tools.
Generation method: RFC 9562 UUIDv1 layout with a monotonic in-session 100-nanosecond timestamp, Web Crypto clock sequence, and Web Crypto random node. RFC 9562 replaced RFC 4122; “RFC 4122 UUID” remains common backward-compatible terminology. Last reviewed: 15 July 2026. Read UUIDv1 in RFC 9562.
Implementation examples
Library behavior varies. Verify whether a UUID v1 library uses a random node or a real MAC address before using it with public data.
Node.js
import { v1 as uuidv1 } from 'uuid';
const identifier = uuidv1();Python
import uuid
identifier = uuid.uuid1() # May use the machine MAC address.Java
import com.fasterxml.uuid.Generators;
UUID identifier = Generators.timeBasedGenerator().generate(); // Check node configuration.PostgreSQL
INSERT INTO events (id) VALUES ('f81d4fae-7dec-11d0-a765-00a0c91e6bf6'::uuid);UUID v1 FAQ
What is the difference between RFC 9562 and RFC 4122?
RFC 9562 is the current UUID standard and replaced RFC 4122 in 2024. UUID v1 keeps the same compatible version, variant, timestamp, clock-sequence, and node layout, so older references to an RFC 4122 UUID v1 describe the same wire format.
What is the difference between a UUID and a GUID?
UUID is the standards term. GUID is Microsoft terminology commonly used for the same 128-bit identifier format; textual casing or braces may differ by convention.
Does UUID v1 expose my MAC address?
A v1 implementation may place a real MAC address in its node field. This browser cannot read your MAC address: it creates a random 48-bit node with the multicast bit set using Web Crypto, unless you explicitly enter a custom node.
How do I extract the timestamp from a UUID v1?
Reassemble time_hi, time_mid, and time_low into the 60-bit Gregorian timestamp, subtract 122,192,928,000,000,000 ticks, and divide by 10,000 for Unix milliseconds. The inspector performs this calculation and shows UTC and local time.
Do UUID v1 values sort chronologically?
Not reliably as canonical strings over longer periods. UUID v1 rearranges the timestamp into time_low, time_mid, and time_hi fields, so sort by the decoded timestamp or use UUID v7 for new time-ordered keys.
How does UUID v1 prevent collisions?
UUID v1 combines a 60-bit timestamp, a 14-bit clock sequence, and a 48-bit node. This tool also advances the timestamp within a session when multiple values would otherwise use the same tick, but applications should still enforce uniqueness where it matters.
Should I use UUID v1, v4, or v7?
Use v7 for new time-ordered database keys, v4 for opaque general-purpose identifiers, and v1 for legacy compatibility or systems that specifically require its timestamp and node layout. UUIDs are identifiers, not secrets or authentication tokens.
What is the batch limit?
You can generate up to 1,000 UUIDs per batch. Large results are rendered in chunks to keep the page responsive.
Does UUID generation leave my device?
No. Generation, inspection, copying, and export happen locally in your browser. The random node and clock sequence come from the browser Web Crypto API.