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Universally Unique Lexicographically Sortable Identifier

Build Status Language (Rust)

UUID can be suboptimal for many uses-cases because:

Instead, herein is proposed ULID:

Implementations in other languages

From the community!

LanguageAuthor
Javascriptalizain
Erlangsavonarola
Elixirmerongivian
Goimdario
JavaLewiscowles1986
Juliaararslan
.NETRobThree
.NETfvilers
PHPLewiscowles1986
Pythonmdipierro
Rubyrafaelsales

Specification

Below is the current specification of ULID as implemented in this repository.

 01AN4Z07BY      79KA1307SR9X4MV3

|----------|    |----------------|
 Timestamp          Randomness
  10 chars           16 chars
   50bits             80bits
   base32             base32

Components

Timestamp

Randomness

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

Encoding

Crockford's Base32 is used as shown. This alphabet excludes the letters I, L, O, and U to avoid confusion and abuse.

0123456789ABCDEFGHJKMNPQRSTVWXYZ

Binary Layout and Byte Order

The components are encoded as 16 octets. Each component is encoded with the Most Significant Byte first (network byte order).

0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                      32_bit_uint_time_low                     |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     16_bit_uint_time_high     |       16_bit_uint_random      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                       32_bit_uint_random                      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                       32_bit_uint_random                      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

String Representation

ttttttttttrrrrrrrrrrrrrrrr

where
t is Timestamp
r is Randomness

Prior Art

Partly inspired by: