Skip to content

Latest commit

 

History

History
167 lines (123 loc) · 5.51 KB

README.md

File metadata and controls

167 lines (123 loc) · 5.51 KB
Raw



ulid


Build Status codecov

Universally Unique Lexicographically Sortable Identifier

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:

  • 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)

JavaScript

Installation

npm install --save ulid

Usage

import ulid from 'ulid'

ulid() // 01ARZ3NDEKTSV4RRFFQ69G5FAV

Implementations in other languages

From the community!

Language Author Binary Implementation
C++ suyash ✓
Objective-C ricardopereira
Crystal SuperPaintman
Delphi matinusso
Erlang savonarola
Elixir merongivian
Go imdario
Go oklog ✓
Java huxi ✓
Java azam
Java Lewiscowles1986
Julia ararslan
.NET RobThree ✓
.NET fvilers
Perl 5 bk ✓
PHP Lewiscowles1986
Python mdipierro
Ruby rafaelsales
Rust mmacedoeu ✓

Specification

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

Note: the binary format has not been implemented.

 01AN4Z07BY      79KA1307SR9X4MV3

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

Components

Timestamp

  • 48 bit integer
  • UNIX-time in milliseconds
  • Won't run out of space till the year 10895 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

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_high                    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     16_bit_uint_time_low      |       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:

Test Suite

npm test

Performance

npm run perf

ulid
336,331,131 op/s » encodeTime
102,041,736 op/s » encodeRandom
17,408 op/s » generate


Suites:  1
Benches: 3
Elapsed: 7,285.75 ms