Che differenza c'è tra UUID v4 e ULID?

UUID v4 è generato in modo completamente casuale e non è ordinabile cronologicamente. ULID incorpora invece un timestamp nella sua struttura, quindi ID generati in sequenza risultano naturalmente ordinabili, oltre a essere univoci.

Gli identificatori generati vengono salvati o inviati a un server?

No, la generazione avviene interamente nel browser tramite l'API crypto nativa: nessun UUID o ULID generato viene inviato o registrato altrove.

Posso generare più identificatori contemporaneamente?

Sì, è possibile generare più UUID o ULID in un colpo solo, utile per popolare rapidamente dati di test.

Free Online UUID Generator — Generate UUID v4 and ULID

What is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit identifier in the format xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx. Version 4 is generated with cryptographically secure random numbers — the collision probability between two UUID v4 is astronomically low.

UUIDs are used as primary keys in databases, document IDs in Firestore (although Firebase prefers push() or doc() auto-IDs), session tokens, and anywhere you need a unique ID without central coordination.

UUID or Firebase auto-ID — which to use with Firestore?

Firebase automatically generates secure random IDs with db.collection('items').doc() — they're optimized to avoid query hotspots. UUIDs are preferable when you need to generate the ID client-side before writing the document, or when integrating with external systems.

How do I generate a UUID in JavaScript without libraries?

With the Web Crypto API: crypto.randomUUID() — available in modern browsers and Node.js 14.17+. Alternatively: ([1e7]+-1e3+-4e3+-8e3+-1e11).replace(/[018]/g,c=>(c^crypto.getRandomValues(new Uint8Array(1))[0]&15>>c/4).toString(16)).

When to use a UUID or ULID generator

This tool generates unique UUID v4 and ULID identifiers, one or several at a time, in standard, uppercase, or no-dashes format, processing everything locally in your browser.

When to use it

You need to generate a unique identifier for a database record, a primary key, or an object in an application.

You need to generate several UUIDs at once to populate test or mock data.

You want a ULID instead of a UUID when you need a chronologically sortable identifier.

When NOT to use it

You need readable sequential IDs (e.g. #1, #2, #3): UUIDs and ULIDs are designed to be globally unique, not short or readable like incremental counters.

Alternatives

Database auto-increment IDs when you need simplicity and readability more than distributed global uniqueness.

nanoid or short UUID when you need a unique identifier that's shorter than a standard UUID.

Common mistakes

Confusing UUID v4 (random) with other UUID versions (v1, v5) that are based on timestamps or namespaces: if you need specific behavior, check which version you actually need.

Using a UUID when readability or chronological ordering matters more: in that case ULID, which embeds a sortable timestamp, is often a better fit.

Frequently asked questions about UUID and ULID generators

UUID v4 is generated completely at random and isn't chronologically sortable. ULID, on the other hand, embeds a timestamp in its structure, so IDs generated in sequence come out naturally sortable, in addition to being unique.

No, generation happens entirely in your browser via the native crypto API: no generated UUID or ULID is ever sent or logged anywhere.

Yes, you can generate several UUIDs or ULIDs in one go, useful for quickly populating test data.

🆔 UUID Generator