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)
nimble install ulid
import ulid
ulid()From the community!
| Language | Author | Binary Implementation |
|---|---|---|
| C++ | suyash | ✓ |
| Objective-C | ricardopereira | |
| Crystal | SuperPaintman | |
| Dart | isoos | ✓ |
| Delphi | matinusso | |
| Erlang | savonarola | |
| Elixir | merongivian | |
| Go | imdario | |
| Go | oklog | ✓ |
| Haskell | steven777400 | |
| Java | huxi | ✓ |
| Java | azam | |
| Java | Lewiscowles1986 | |
| Julia | ararslan | |
| Lua | Tieske | |
| .NET | RobThree | ✓ |
| .NET | fvilers | |
| Nim | adelq | |
| Perl 5 | bk | ✓ |
| PHP | Lewiscowles1986 | |
| Python | mdipierro | |
| Ruby | rafaelsales | |
| Rust | mmacedoeu | ✓ |
| Rust | dylanhart | ✓ |
| Swift | simonwhitehouse | |
| Tcl | dbohdan |
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
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
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
Crockford's Base32 is used as shown. This alphabet excludes the letters I, L, O, and U to avoid confusion and abuse.
0123456789ABCDEFGHJKMNPQRSTVWXYZ
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 |
+-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-+
ttttttttttrrrrrrrrrrrrrrrr
where
t is Timestamp
r is Randomness
Inspired by:
Partly inspired by:
- http://instagram-engineering.tumblr.com/post/10853187575/sharding-ids-at-instagram
- https://firebase.googleblog.com/2015/02/the-2120-ways-to-ensure-unique_68.html
nimble test
nimble perf
ulid.nim time/iter iters/s
============================================================================
encode_time 319.93ns 3.13M
encode_random 3.57us 280.33K
ulid 3.85us 259.78K