uuidv7

An experimental implementation of the proposed UUID Version 7

import { uuidv7 } from "uuidv7";

const result = uuidv7(); // e.g., "017fe537-bb13-7c35-b52a-cb5490cce7be"

On browsers and Deno:

import { uuidv7 } from "https://unpkg.com/uuidv7@^0.5";

const result = uuidv7(); // e.g., "017fe537-bb13-7c35-b52a-cb5490cce7be"

Command-line interface:

npx uuidv7

See draft-ietf-uuidrev-rfc4122bis-09.

Field and bit layout

This implementation produces identifiers with the following bit layout:

 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                          unix_ts_ms                           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|          unix_ts_ms           |  ver  |        counter        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|var|                        counter                            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                             rand                              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Where:

• The 48-bit unix_ts_ms field is dedicated to the Unix timestamp in milliseconds.
• The 4-bit ver field is set at 0111.
• The 42-bit counter field accommodates a counter that ensures the increasing order of IDs generated within a millisecond. The counter is incremented by one for each new ID and is reset to a random number when the unix_ts_ms changes.
• The 2-bit var field is set at 10.
• The remaining 32 rand bits are filled with a cryptographically strong random number.

The 42-bit counter is sufficiently large, so you do not usually need to worry about overflow, but in an extremely rare circumstance where it overflows, this library increments the unix_ts_ms field. As a result, the unix_ts_ms may have a greater value than that of the system's real-time clock.

UUIDv7, by design, heavily relies on the system's wall clock to guarantee the monotonically increasing order of generated IDs. A generator may not be able to produce a monotonic sequence if the system clock goes backwards. This library ignores a clock rollback and freezes the previously used unix_ts_ms unless the clock rollback is considered significant (by more than ten seconds). If such a significant rollback takes place, this library resets the generator and thus breaks the monotonic order of generated IDs.

Other features

This library also supports the generation of UUID version 4:

import { uuidv4 } from "uuidv7";

const result = uuidv4(); // e.g., "83229083-75c3-4da5-8378-f88ef1a2bcd1"

uuidv7obj() and uuidv4obj() return an object that represents a UUID as a 16-byte byte array:

import { uuidv7obj } from "uuidv7";

const object = uuidv7obj();
console.log(object.bytes); // Uint8Array(16) [ ... ]
console.log(String(object)); // e.g., "017fea6b-b877-7aef-b422-57db9ed15e9d"

console.assert(object.getVariant() === "VAR_10");
console.assert(object.getVersion() === 7);

console.assert(object.clone().equals(object));
console.assert(object.compareTo(uuidv7obj()) < 0);

The V7Generator primitive allows to utilize a separate counter state from that of the global generator. It also provides a fallible variant of the generator function to give an absolute guarantee of the increasing order of UUIDs despite a significant rollback of the system timestamp source.

import { V7Generator } from "uuidv7";

const g = new V7Generator();
const x = g.generate();
const y = g.generateOrAbort();
if (y === undefined) {
  throw new Error("The clock went backwards by ten seconds!");
}
console.assert(x.compareTo(y) < 0);

See the API documentation for details.

CommonJS support

The CommonJS entry point is deprecated and provided for backward compatibility purposes only. The entry point is no longer tested and will be removed once this library hits the stable version number of v1.

License

Licensed under the Apache License, Version 2.0.