@thi.ng/ksuid

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• About
  • CLI usage
• Status
  • Breaking changes
• Related packages
• Installation
• Dependencies
• API
• Benchmarks
• Authors
• License

About

Configurable K-sortable unique IDs, ULIDs, binary & base-N encoded, 32/48/64bit time resolutions.

Idea based on segmentio/ksuid, though the added flexibility in terms of configuration & implementation also enables the creation of ULIDs:

Feature	KSUID default	ULID default
Configurable bit size	160 bits	128 bits
Base-N encoding scheme	base62(1)	base32 (Crockford)
Timestamp resolution	seconds (32 bits)	milliseconds (48 bits)
	milliseconds (64 bits)
Epoch start time offset	approx. 2020-09-13(2)	none
Time-only base ID generation	✅	✅
ID parsing / decomposition	✅	✅
Configurable RNG source(3)	✅	✅

• ⁽¹⁾ See @thi.ng/base-n for alternatives
• ⁽²⁾ With the default offset, the max. supported date for KSUID32 is 2156-10-20T18:54:55Z
• ⁽³⁾ Default: window.crypto, Math.random as fallback

IDs generated w/ this package are composed of a 32, 48 or 64 bit Unix epochs and N additional bits of a random payload (from a configurable source). By default all timestamps are shifted to free up bits for the future. IDs can be generated as byte arrays or base-N encoded strings. For the latter, the JS runtime MUST support BigInt.

CLI usage

Since v3.1.0 a small CLI for ad-hoc KSUID generation is included. Currently only KSUID32 is supported and IDs are always based on the current time:

npx @thi.ng/ksuid
# 0dwncLZE8byaQdccncWDmsNmlYt

# optionally provide number of random bytes to be used (default: 16)
npx @thi.ng/ksuid 8
# 01ogp9KDpWlQ0pXCY

Status

STABLE - used in production

Search or submit any issues for this package

Breaking changes

Since v3.0.0 all epoch time-shift config values are to be given in milliseconds. This change is unifying this behavior and is only a breaking change if using KSUID32 and specifying custom epoch offsets (using defaults is not impacted). Previously, KSUID32 used an offset given in seconds, whereas the other implementations already used milliseconds.

Related packages

• @thi.ng/base-n - Arbitrary base-n conversions w/ presets for base8/16/32/36/58/62/64/83/85, support for bigints and encoding/decoding of byte arrays
• @thi.ng/idgen - Generator of opaque numeric identifiers with optional support for ID versioning and efficient re-use
• @thi.ng/random - Pseudo-random number generators w/ unified API, distributions, weighted choices, ID generation

Installation

yarn add @thi.ng/ksuid

ESM import:

import * as ksuid from "@thi.ng/ksuid";

Browser ESM import:

<script type="module" src="https://esm.run/@thi.ng/ksuid"></script>

JSDelivr documentation

For Node.js REPL:

const ksuid = await import("@thi.ng/ksuid");

Package sizes (brotli'd, pre-treeshake): ESM: 990 bytes

Dependencies

• @thi.ng/base-n
• @thi.ng/errors
• @thi.ng/random
• @thi.ng/strings

API

Generated API docs

import { defKSUID32, defKSUID64, defULID } from "@thi.ng/ksuid";

// init 32bit epoch (resolution: seconds) w/ defaults
const id = defKSUID32();
// init 64bit epoch (resolution: milliseconds), same API
const id = defKSUID64();
// init 48bit epoch (resolution: milliseconds), same API
const id = defULID();

id.next();
// '05XCWbXa3akRqLDBUw4ogCVKGkd'

const a = id.nextBinary()
// Uint8Array(20) [
//     0, 160,  48, 77, 101, 251,
//   244,  17, 155, 97,  24, 101,
//    70,  71, 207, 23,  32,  21,
//   244, 116
// ]

// format a binary KSUID
id.format(a);
// '05XCZ32AaDZfZt0SWE2C22o6cqK'

id.parse("05XCZ32AaDZfZt0SWE2C22o6cqK")
// {
//   epoch: 1610498125000,
//   id: Uint8Array(16) [
//     101, 251, 244,  17, 155, 97,
//      24, 101,  70,  71, 207, 23,
//      32,  21, 244, 116
//   ]
// }

new Date(1610498125000).toISOString()
// '2021-01-13T00:35:25.000Z'

Creating custom IDs:

import { BASE36 } from "@thi.ng/base-n";

// using base36, no time shift, 64bit random part
const id36 = defKSUID32({ base: BASE36, epoch: 0, bytes: 8 });

id36.next();
// '2VOUKH4K59AG0RXR4XH'

Benchmarks

Benchmarks can be run via yarn bench. All timings in milliseconds (test config: Node v20.4.0, MBA M1 2021, 16GB). The benchmark collects N KSUIDs w/ different configs in an array, with each case being run 100 times.

Title	Iter	Size	Total	Mean	Median	Min	Max	Q1	Q3	SD%
b62, 128bit, n=10000	100	1	2158.68	21.59	21.57	19.91	25.91	20.42	21.87	6.26
b62, 64bit, n=10000	100	1	1200.40	12.00	11.95	11.27	14.66	11.82	12.10	3.99

Authors

• Karsten Schmidt

If this project contributes to an academic publication, please cite it as:

@misc{thing-ksuid,
  title = "@thi.ng/ksuid",
  author = "Karsten Schmidt",
  note = "https://thi.ng/ksuid",
  year = 2020
}

License

© 2020 - 2025 Karsten Schmidt // Apache License 2.0