Inspect UUID and ULID versions, timestamps, variants, and canonical representations.
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About UUID / ULID Decoder
Inspects a UUID or ULID and shows what it encodes: the UUID version and variant, the embedded creation time for v1, v6, v7 and ULIDs, the clock sequence and node for v1/v6, and the random fields of v7. Hyphenated, unhyphenated, braced and urn:uuid: forms are accepted, and the same 128 bits are shown as canonical UUID, GUID, URN, ULID, Base64, Base64URL, decimal and a byte array. Buttons generate fresh v1, v4 and v7 samples.
Common uses
- Find out when a UUIDv7 or ULID primary key was created
- Check which UUID version a library or database generates
- Convert a UUID to a ULID or Base64 for a shorter representation
- Verify that a value is a valid RFC 9562 UUID
FAQ
- Can I get a timestamp from a UUID?
- Only from time-based versions. v1 and v6 embed a 60-bit count of 100-nanosecond intervals since 1582-10-15, and v7 embeds a 48-bit Unix timestamp in milliseconds. v4 is random and v3/v5 are hashes, so they contain no time.
- What is the difference between UUIDv4 and UUIDv7?
- v4 has 122 random bits. v7 starts with a millisecond Unix timestamp followed by random bits, so v7 values sort by creation time, which keeps database index inserts mostly sequential.
- What is a ULID?
- A ULID is a 128-bit identifier written as 26 Crockford Base32 characters: a 48-bit millisecond timestamp followed by 80 random bits. Like UUIDv7 it sorts lexicographically by creation time.
- Can I recover the name from a UUIDv3 or v5?
- No. v3 and v5 are built from an MD5 or SHA-1 hash of a namespace and name, and a hash cannot be reversed.