ulid: Generate Universally Unique Lexicographically Sortable...
In ulid: Generate Universally Unique Lexicographically Sortable Identifiers

Description Details Author(s)

(grifted from https://github.com/ulid/spec)

UUID can be suboptimal for many uses-cases because:

It isn't the most character efficient way of encoding 128 bits of randomness
UUID v1/v2 is impractical in many environments, as it requires access to a unique, stable MAC address
UUID v3/v5 requires a unique seed and produces randomly distributed IDs, which can cause fragmentation in many data structures
UUID v4 provides no other information than randomness which can cause fragmentation in many data structures

Instead, herein is proposed ULID:

1	ulid() // 01ARZ3NDEKTSV4RRFFQ69G5FAV

128-bit compatibility with UUID
1.21e+24 unique ULIDs per millisecond
Lexicographically sortable!
Canonically encoded as a 26 character string, as opposed to the 36 character UUID
Uses Crockford's base32 for better efficiency and readability (5 bits per character)
Case insensitive
No special characters (URL safe)
Monotonic sort order (correctly detects and handles the same millisecond)

01AN4Z07BY      79KA1307SR9X4MV3

|----------|    |----------------|
  Timestamp          Randomness
   48bits              80bits

Components

Timestamp

48 bit integer
UNIX-time in milliseconds
Won't run out of space till the year 10889 AD.

Randomness

80 bits
Cryptographically secure source of randomness, if possible

Sorting

The left-most character must be sorted first, and the right-most character sorted last (lexical order). The default ASCII character set must be used. Within the same millisecond, sort order is not guaranteed.