# UUID generator and decoder (v4, v7)

> Generate reproducible UUID v4 and v7 values from a seed, or validate any UUID or GUID and decode its version, variant and embedded timestamp.

ಸಂವಾದಾತ್ಮಕ ಆವೃತ್ತಿ: https://www.calcopenly.com/kn/programming/uuid-decoder-generator
ವಿಷಯ: ಪ್ರೋಗ್ರಾಮಿಂಗ್ ಮತ್ತು ತಂತ್ರಜ್ಞಾನದ ಕ್ಯಾಲ್ಕುಲೇಟರ್‌ಗಳು

A UUID is a 128-bit identifier written as 32 hex digits in 8-4-4-4-12 groups. RFC 9562 fixes two fields in every standard UUID: the variant bits 10 at the start of the 17th hex digit, and a 4-bit version number in the 13th. The decoder reads both, then unpacks what that version carries: a 48-bit Unix millisecond timestamp for version 7, a 60-bit count of 100-nanosecond intervals since 15 October 1582 for versions 1 and 6, or 122 random bits for version 4.

The default is the RFC 9562 version 7 example, 017f22e2-79b0-7cc3-98c4-dc0c0c07398f, whose first 48 bits count 1,645,557,742,000 ms, which is 22 February 2022 at 19:22:22 UTC. Developers pick v7 for database keys because the values sort by creation time.

Generated UUIDs come from a seeded xoshiro256** generator, so the same seed always gives the same list. For identifiers that must be unguessable, use a cryptographic source such as crypto.randomUUID().

## ಒಳಾಂಶಗಳು

- **I want to** (ಆಯ್ಕೆಗಳು: Decode a UUID, Generate UUIDs)
- **UUID**: Upper or lower case, with or without hyphens, braces or a urn:uuid: prefix.
- **Version** (ಆಯ್ಕೆಗಳು: v4 (random), v7 (time-ordered))
- **Seed**: A whole number from 0 to 2^64 − 1; the same seed always gives the same UUIDs.
- **How many**
- **Timestamp date (UTC)**
- **Timestamp time (UTC)**

## ಫಲಿತಾಂಶಗಳು

- UUID — ಮುಖ್ಯ ಫಲಿತಾಂಶ
- Type
- Version
- Variant
- Embedded time
- Unix time (ms)
- Clock sequence
- Node
- Generated UUIDs

## ಸೂತ್ರ

$$
\begin{aligned} \text{v7: } t_{ms} &= \text{bits } 0\text{–}47 \\ \text{v1/v6: } t &= \frac{\text{60-bit count}}{10^7} \\ &\quad - 12\,219\,292\,800\ \text{s} \end{aligned}
$$

## ಪರಿಹರಿಸಿದ ಉದಾಹರಣೆಗಳು

### RFC 9562 version 7 example

- I want to: Decode a UUID
- UUID: 017F22E2-79B0-7CC3-98C4-DC0C0C07398F
- **UUID: 017f22e2-79b0-7cc3-98c4-dc0c0c07398f**
- **Version: 7**
- **Variant: RFC 9562**
- **Embedded time: 2022-02-22 19:22:22.000 UTC**
- **Unix time: 1645557742000 ms**
- ಪರಿಶೀಲನೆಯ ಮೂಲ: RFC 9562 Appendix A.6 (Tuesday, February 22, 2022 2:22:22.00 PM GMT-05:00); Python 3.8: int('017F22E279B0', 16) = 1645557742000

### RFC 9562 version 4 example

- I want to: Decode a UUID
- UUID: 919108f7-52d1-4320-9bac-f847db4148a8
- **Version: 4**
- **Type: Random**
- **Variant: RFC 9562**
- ಪರಿಶೀಲನೆಯ ಮೂಲ: RFC 9562 Appendix A.3; Python 3.8 uuid.UUID(...).version = 4, .variant = 'specified in RFC 4122'

### RFC 9562 version 1 example

- I want to: Decode a UUID
- UUID: C232AB00-9414-11EC-B3C8-9F6BDECED846
- **Version: 1**
- **Embedded time: 2022-02-22 19:22:22.0000000 UTC**
- **Clock sequence: 13,256**
- **Node: 9f:6b:de:ce:d8:46**
- ಪರಿಶೀಲನೆಯ ಮೂಲ: RFC 9562 Appendix A.1; Python 3.8 uuid.UUID(...).time = 138648505420000000, (time − 122192928000000000) / 10^7 = 1645557742 s; .clock_seq = 13256; .node = 0x9f6bdeced846

### RFC 9562 version 6 example

- I want to: Decode a UUID
- UUID: 1EC9414C-232A-6B00-B3C8-9F6BDECED846
- **Version: 6**
- **Embedded time: 2022-02-22 19:22:22.0000000 UTC**
- ಪರಿಶೀಲನೆಯ ಮೂಲ: RFC 9562 Appendix A.5 (same instant as the v1 example)

### Nil UUID with braces and a URN prefix (edge)

- I want to: Decode a UUID
- UUID: urn:uuid:{00000000-0000-0000-0000-000000000000}
- **UUID: 00000000-0000-0000-0000-000000000000**
- **Type: Nil UUID**
- ಪರಿಶೀಲನೆಯ ಮೂಲ: RFC 9562 §5.9 (Nil UUID: all 128 bits zero) and §4 (urn:uuid: form)

### Max UUID (edge)

- I want to: Decode a UUID
- UUID: FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
- **UUID: ffffffff-ffff-ffff-ffff-ffffffffffff**
- **Type: Max UUID**
- ಪರಿಶೀಲನೆಯ ಮೂಲ: RFC 9562 §5.10 (Max UUID: all 128 bits one)

## ಪ್ರಶ್ನೆಗಳು

### What is the difference between UUID v4 and v7?

Version 4 fills 122 of the 128 bits with random data, so values are spread evenly and reveal nothing. Version 7, defined in RFC 9562 (May 2024), puts a 48-bit Unix millisecond timestamp first and 74 random bits after it, so new IDs sort in creation order. RFC 9562 notes that v4 has poor database-index locality, which is why v7 suits primary keys, at the cost of revealing when each ID was made.

### Can two random UUIDs collide?

In practice, no. A v4 UUID has 122 random bits, so by the birthday bound you would need about 2.7 × 10^18 of them for a 50% chance of a single duplicate, or about 103 trillion for a one-in-a-billion chance. Real collisions come from faulty random number generators or reused seeds, which is why the seeded UUIDs here shouldn't be used where uniqueness across systems matters.

### What is the difference between a UUID and a GUID?

They are the same 128-bit format; GUID is Microsoft's name for it. Microsoft tools often print GUIDs in upper case inside braces, such as {017F22E2-79B0-7CC3-98C4-DC0C0C07398F}, and RFC 9562 allows upper, lower or mixed case, so parsers should accept both. The one real difference is binary byte order: Windows stores the first three groups little-endian, which matters only when reading raw bytes.

### How do I get the timestamp from a UUID v7?

Take the first 12 hex digits, which hold a 48-bit count of milliseconds since 1970-01-01 00:00 UTC, and convert them to decimal. For 017f22e2-79b0-7cc3-98c4-dc0c0c07398f, 017f22e279b0 is 1,645,557,742,000 ms, which is 2022-02-22 19:22:22.000 UTC. The 48-bit field runs out in the year 10889, so it will not wrap in practice.

### Is a version 1 UUID a privacy risk?

It can be. Version 1 stores a 60-bit timestamp and a 48-bit node field that is traditionally the machine's MAC address, so the ID reveals when and on which network card it was made; the RFC 9562 v1 example decodes to 2022-02-22 19:22:22 UTC with node 9f:6b:de:ce:d8:46. RFC 9562 allows a random node value instead, and says to use version 7 instead of 1 or 6 where possible.

### “UUID generator and decoder (v4, v7)” ಎಷ್ಟು ನಿಖರವಾಗಿದೆ?

ನಿಖರತೆ ನಿಮ್ಮ ಇನ್‌ಪುಟ್‌ಗಳು ಮತ್ತು ವಿಧಾನದ ಊಹೆಗಳನ್ನು ಅವಲಂಬಿಸಿದೆ. ದಶಮಾಂಶ ಗಣನೆ 50 ಸಾರ್ಥಕ ಅಂಕೆಗಳನ್ನು ಬಳಸುತ್ತದೆ. ಆದರೆ ಅಂದಾಜುಗಳು, ಸಂಖ್ಯಾತ್ಮಕ ವಿಧಾನಗಳು ಮತ್ತು ಮೂಲ ದತ್ತಾಂಶ ಕಡಿಮೆ ನಿಖರವಾಗಿರಬಹುದು; ಪ್ರದರ್ಶಿತ ಮೌಲ್ಯಗಳನ್ನು ರೌಂಡ್ ಮಾಡುವುದರಿಂದ ಈ ಮಿತಿಗಳು ನಿವಾರಣೆಯಾಗುವುದಿಲ್ಲ. ಸ್ವತಂತ್ರ ಮೂಲಗಳ ಪರಿಹಾರಗಳೊಂದಿಗೆ ಪರಿಶೀಲಿಸಿದ ಉದಾಹರಣೆಗಳು: 8. ಉದಾಹರಣೆಗೆ, “RFC 9562 version 7 example” ಅನ್ನು RFC 9562 Appendix A.6 (Tuesday, February 22, 2022 2:22:22.00 PM GMT-05:00); Python 3.8: int('017F22E279B0', 16) = 1645557742000 ಜೊತೆಗೆ ಪರಿಶೀಲಿಸಲಾಗುತ್ತದೆ.

### ಈ ವಿಧಾನದ ಮೂಲ ಯಾವುದು?

RFC 9562 — Universally Unique IDentifiers (UUIDs), §4–5 and Appendix A test vectors; Blackman & Vigna — xoshiro256** and SplitMix64 reference code.

## ಮೂಲಗಳು

- [RFC 9562 — Universally Unique IDentifiers (UUIDs), §4–5 and Appendix A test vectors](https://www.rfc-editor.org/rfc/rfc9562)
- [Blackman & Vigna — xoshiro256** and SplitMix64 reference code](https://prng.di.unimi.it/)