UUID Decoder & Validator - Extract UUID Information

What is UUID Decoding?

UUID decoding is the process of analyzing a UUID to extract information about its:

Version: Which UUID version (1-8) based on 4 bits in position 48-51
Variant: Which UUID variant (usually RFC 4122) based on bits 64-65
Components: Extracting timestamp, node ID, or other data based on version
Generation time: For time-based UUIDs (v1, v6, v7)

Example: 123e4567-e89b-12d3-a456-426614174000 is a Version 1 UUID created on 2018-10-03 09:45:32 UTC.

UUID Structure Overview

Format	Description
8-4-4-4-12	32 hex digits grouped with hyphens
Version bits	Bits 48-51 (13th digit)
Variant bits	Bits 64-65 (17th digit)

The version number appears as the first hex digit in the third group (e.g., 123e4567-e89b-12d3-a456-426614174000 for version 1).

Decoding by UUID Version

Version	What can be decoded
UUID v1	Timestamp (with 100ns precision, since Oct 15, 1582) MAC address (if not randomized) Clock sequence (for collision avoidance)
UUID v3/v5	Cannot decode original input Can verify if created from known inputs Can distinguish between v3 (MD5) and v5 (SHA-1)
UUID v4	Random data only No extractable information Can verify it's a valid v4 UUID
UUID v6	Timestamp (with 100ns precision, since Oct 15, 1582) MAC address (if not randomized) Clock sequence (for collision avoidance)
UUID v7	Unix timestamp (millisecond precision) Random component (not decodable)
ULID	Unix timestamp (millisecond precision) Random component (not decodable)

Timestamp Extraction from UUIDs

UUID Type	Time Extraction Method	Epoch
UUID v1	Combine bits 0-31, 32-47, and 48-59, reordering timestamp components	October 15, 1582
UUID v6	Extract bits 0-59 (already in correct order)	October 15, 1582
UUID v7	Extract bits 0-47 (Unix milliseconds)	January 1, 1970
ULID	Decode first 10 Base32 characters to get 48-bit Unix milliseconds	January 1, 1970

UUID Validation Rules

Format check: 8-4-4-4-12 hexadecimal digits with hyphens
Version check: 13th character must be 1-8
Variant check: 17th character must be 8, 9, A, or B (for RFC 4122)

Regular expression for basic UUID validation:

^[0-9a-f]8-[0-9a-f]4-[1-8][0-9a-f]3-[89ab][0-9a-f]3-[0-9a-f]12$

Practical Applications

Forensic analysis: Determining when IDs were created
Debugging: Tracing system behavior through ID timestamps
Auditing: Validating chronological integrity
Security analysis: Detecting forged or manipulated IDs
Data recovery: Reconstructing temporal relationships
System migrations: Understanding legacy UUID implementation details

MAC Address Extraction (v1/v6)

For UUID v1 and v6, you can often extract the node identifier (MAC address) if it wasn't randomized during generation:

Extract the last 12 hex digits (48 bits) from the UUID
Format with colons as XX:XX:XX:XX:XX:XX
Check if the MAC address is real or random by examining the multicast bit

If the first byte has bit 0x01 set, it's likely a randomized node ID rather than an actual MAC address.

Frequently Asked Questions

Can I determine exactly when a UUID v4 was created?

No. UUID v4 is purely random with no timestamp information. Time of creation cannot be determined from a UUID v4 value.

How accurate are timestamps in time-based UUIDs?

UUID v1/v6 timestamps have 100-nanosecond precision. UUID v7 and ULID have millisecond precision. However, actual system clock accuracy may vary.

Can I convert between UUID versions?

No, you cannot convert directly between versions while preserving the same identifier value. Different versions have fundamentally different structures.

Can I identify the computer that generated a UUID v1?

If the node ID wasn't randomized, a UUID v1 may contain the MAC address of the generating system. However, many modern implementations randomize this for privacy.

How can I tell if a UUID is valid?

Check the format (8-4-4-4-12 hex digits), verify the version digit (13th character) is 1-8, and confirm the variant bits (17th character is 8, 9, A, or B for RFC 4122 UUIDs).

UUID Decoder and Validator

Try these examples: