# 
[](https://www.npmjs.com/package/@thi.ng/ksuid)
[](https://mastodon.thi.ng/@toxi)
> [!NOTE]
> This is one of 205 standalone projects, maintained as part
> of the [@thi.ng/umbrella](https://github.com/thi-ng/umbrella/) monorepo
> and anti-framework.
>
> 🚀 Please help me to work full-time on these projects by [sponsoring me on
> GitHub](https://github.com/sponsors/postspectacular). Thank you! ❤️
- [About](#about)
- [CLI usage](#cli-usage)
- [Status](#status)
- [Breaking changes](#breaking-changes)
- [Related packages](#related-packages)
- [Installation](#installation)
- [Dependencies](#dependencies)
- [API](#api)
- [Benchmarks](#benchmarks)
- [Authors](#authors)
- [License](#license)
## About
Configurable K-sortable unique IDs, ULIDs, binary & base-N encoded, 32/48/64bit time resolutions.
Idea based on [segmentio/ksuid](https://github.com/segmentio/ksuid), though the
added flexibility in terms of configuration & implementation also enables the
creation of [ULIDs](https://github.com/ulid/spec):
| 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](https://github.com/thi-ng/umbrella/tree/develop/packages/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`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/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:
```bash
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](https://github.com/thi-ng/umbrella/issues?q=%5Bksuid%5D+in%3Atitle)
### Breaking changes
Since v3.0.0 all
[`epoch`](https://docs.thi.ng/umbrella/ksuid/interfaces/KSUIDOpts.html#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](https://github.com/thi-ng/umbrella/tree/develop/packages/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](https://github.com/thi-ng/umbrella/tree/develop/packages/idgen) - Generator of opaque numeric identifiers with optional support for ID versioning and efficient re-use
- [@thi.ng/random](https://github.com/thi-ng/umbrella/tree/develop/packages/random) - Pseudo-random number generators w/ unified API, distributions, weighted choices, ID generation
## Installation
```bash
yarn add @thi.ng/ksuid
```
ESM import:
```ts
import * as ksuid from "@thi.ng/ksuid";
```
Browser ESM import:
```html
```
[JSDelivr documentation](https://www.jsdelivr.com/)
For Node.js REPL:
```js
const ksuid = await import("@thi.ng/ksuid");
```
Package sizes (brotli'd, pre-treeshake): ESM: 990 bytes
## Dependencies
- [@thi.ng/base-n](https://github.com/thi-ng/umbrella/tree/develop/packages/base-n)
- [@thi.ng/errors](https://github.com/thi-ng/umbrella/tree/develop/packages/errors)
- [@thi.ng/random](https://github.com/thi-ng/umbrella/tree/develop/packages/random)
- [@thi.ng/strings](https://github.com/thi-ng/umbrella/tree/develop/packages/strings)
## API
[Generated API docs](https://docs.thi.ng/umbrella/ksuid/)
```ts
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:
```ts
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](https://thi.ng)
If this project contributes to an academic publication, please cite it as:
```bibtex
@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