A ULID (Universally Unique Lexicographically Sortable Identifier) is a 128-bit identifier encoded as a compact 26-character Crockford base32 string. Like UUID v7, it is time-ordered, so ULIDs sort by creation time — but they are shorter and URL-friendly.
This tool generates ULIDs entirely in your browser. They are case-insensitive, contain no special characters, and are safe to use directly in URLs.
ULID structure
A ULID is made of two parts: the first 48 bits encode a Unix millisecond timestamp, and the remaining 80 bits are random. Encoded in Crockford base32, this produces a fixed 26-character string such as 01ARZ3NDEKTSV4RRFFQ69G5FAV.
Because the timestamp comes first, sorting ULIDs as plain text also sorts them chronologically, which is convenient for logs, keys, and event streams.
ULID vs UUID
ULIDs and UUID v7 both give you sortable, time-based identifiers. ULIDs are more compact (26 characters versus 36) and avoid hyphens, making them tidy in URLs and filenames.
UUIDs, however, are an established standard with first-class support in most databases and languages. Choose ULID for compact, URL-safe sortable IDs, and UUID when you need standard UUID format and tooling.
Frequently asked questions
- Are ULIDs sortable?
- Yes. The leading timestamp means ULIDs sort lexicographically in the same order they were created, which is ideal for time-series data and database keys.
- Are ULIDs URL-safe?
- Yes. ULIDs use Crockford base32 with no special characters or hyphens, so they can be placed directly into URLs and file names.
- How long is a ULID?
- A ULID is 128 bits, the same size as a UUID, but encoded as a 26-character string instead of the 36-character UUID format.