UUID / ULID Decoder
Parse and decode UUIDs and ULIDs instantly
Decoded Results
UUID Versions Quick Reference
Paste any UUID or ULID and this decoder instantly breaks it down: version, variant, embedded timestamp, node (MAC) address, and clock sequence where applicable. It’s made for developers debugging database keys, tracing when an identifier was generated, or verifying their UUID library.
How to Use
- Paste the identifier: Drop a UUID (like
550e8400-e29b-41d4-a716-446655440000) or a 26-character ULID into the input field - Read the breakdown: The tool validates the format, detects the version and variant, and extracts every field the identifier carries
- Check the timestamp: For v1, v7, and ULID values, the embedded creation time is shown as a human-readable date
Features
- Automatic UUID version detection (v1 through v8)
- Variant identification: RFC 4122/DCE, Microsoft GUID, NCS, reserved
- Timestamp extraction for v1, v7, and ULID identifiers
- Node/MAC address and clock sequence decoding for v1
- Full ULID support with Crockford Base32 decoding
- 100% client-side — identifiers never leave your browser
What Is a UUID, Exactly?
A UUID is a 128-bit number, conventionally written as 32 hexadecimal digits in five groups separated by hyphens: 8-4-4-4-12. With 2¹²² possible RFC 4122 values, the odds of an accidental collision are astronomically small — you’d need to generate a billion UUIDs per second for about 85 years before a duplicate becomes likely. That property is why UUIDs are everywhere: database primary keys, transaction IDs, file names, session tokens.
Two positions encode metadata. The first digit of the third group is the version nibble — a 4 there means random, a 1 means time-based. The high bits of the fourth group mark the variant, which tells parsers the value follows RFC 4122 rather than an older or vendor-specific layout.
Why the Version Matters
Version 4 UUIDs are pure randomness — nothing to decode beyond their type. Version 1 embeds a 60-bit timestamp counted in 100-nanosecond intervals since October 15, 1582 — the start of the Gregorian calendar — plus the generator’s MAC address, convenient for tracing but a known privacy leak. Version 7, the modern favorite, puts a Unix millisecond timestamp first, so v7 UUIDs sort naturally by creation time and work well as database keys without fragmenting indexes. ULIDs offer the same sortability in a shorter, URL-safe string.
Use Cases
- Debugging: Confirm a UUID library actually generates v4 instead of the v1 you expected
- Forensics: Find out when a record was created from a v1 or v7 primary key
- Security review: Detect v1 UUIDs leaking MAC addresses into public APIs
- Data migration: Validate identifier formats before importing legacy data
Related Tools
Frequently Asked Questions
What is a UUID version?
A UUID version indicates how the UUID was generated. Version 1 uses timestamp and MAC address, version 3 uses MD5 hashing, version 4 is randomly generated, version 5 uses SHA-1 hashing, version 7 uses Unix timestamp with random bits, and so on. Each version has different properties in terms of uniqueness, sortability, and information density.
How do I decode a UUID timestamp?
Only version 1 and version 7 UUIDs contain embedded timestamps. Paste your UUID into the input field and if it is v1 or v7, the timestamp will be automatically extracted and displayed as a human-readable date. The tool handles the conversion from the UUID epoch (October 15, 1582) to standard Unix time.
What is the difference between UUID and ULID?
UUID (Universally Unique Identifier) is a 128-bit value typically represented as 36 characters with dashes. ULID (Universally Unique Lexicographically Sortable Identifier) is a 128-bit value represented as 26 characters using Crockford Base32. ULIDs are designed to be sortable by generation time and are more compact and URL-friendly than UUIDs.