UUID identifiers

What it identifies and guarantees

UUID means universally unique identifier. The format has 128 bits, but uniqueness is not a mathematical guarantee for every generated value: collisions remain possible. Use a database uniqueness constraint when duplicates must be rejected.

Version 4 UUID

Version 4 has 122 random bits; the others identify version and variant. Browser crypto.randomUUID() produces v4 using a cryptographically secure generator. Other UUID versions use different generation methods.

Format

The result is a string of groups separated by hyphens. This illustrates its shape; do not reuse it for every record.

36b8f84d-df4e-4d49-b662-bcde71a8764f

JavaScript usage

In browsers, randomUUID() requires a secure context such as HTTPS. Check availability. Generate a new value for each item, but do not regenerate an existing record’s identifier every time it is displayed.

const article = {
  id: crypto.randomUUID(),
  title: "Introduction to HTML",
};
console.log(article.id);

Identification and permissions

An identifier does not replace access checks. An API receiving a record UUID must still verify the user’s permission. This example is not a complete authentication or account-recovery protocol.

Practice

1. Generate identifiers for three different articles.
2. Check the hexadecimal group lengths: 8-4-4-4-12.
3. Keep the same id when editing an article’s title.