A ULID (Universally Unique Lexicographically Sortable Identifier) is a 128-bit identifier compatible with UUIDs. It consists of a 48-bit millisecond timestamp followed by 80 bits of cryptographic randomness encoded in 26 Crockford Base32 characters.

Why choose ULID over UUID v4?

Unlike standard UUID v4 which is completely random and causes B-tree index fragmentation in SQL databases, ULIDs are time-ordered and sort naturally in chronological order, dramatically improving database indexing and write performance.

Why does Crockford Base32 exclude letters I, L, O, and U?

Crockford's Base32 excludes I and L to prevent visual confusion with the digit 1, O to avoid confusion with 0, and U to prevent accidental profanity formation.

ULID Generator & Timestamp Decoder

Generate Universally Unique Lexicographically Sortable Identifiers (ULID) in bulk and decode Crockford Base32 components back into precise millisecond timestamps. 100% private in-browser.

Enter 26-Character ULID to Decode:

CROCKFORD BASE32 BREAKDOWN:

01ARZ3NDEK

Timestamp (10 chars, 48-bit)

TSV4RRFFQ69G5FAV

Randomness (16 chars, 80-bit)

UTC Timestamp -

Local Timestamp -

Epoch Milliseconds -

Relative Age -

Why Engineering Teams Choose ULID

Monotonically Sortable

ULIDs are millisecond timestamped at the most significant bits, guaranteeing that records inserted over time are stored in sequential order, preventing disk fragmentation.

128-Bit UUID Compatibility

ULIDs store exactly 128 bits of data, making them directly swappable with native binary UUID columns (PostgreSQL UUID, MySQL BINARY(16)).

URL-Safe & Human Readable

Encoded into 26 characters of Crockford's Base32 alphabet without punctuation or hyphens, making them compact and safe for query strings and REST paths.