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UUID Generator

Generate UUID v4 in bulk

About UUID Generator

UUIDs (Universally Unique Identifiers) are 128-bit identifiers standardised in RFC 4122. This tool generates v4 UUIDs — fully random, no central coordinator needed — using the browser's `crypto.randomUUID()` API. v4 is the safe default for almost any use: distributed primary keys, idempotency keys, file names, correlation IDs. If you specifically need time-ordered UUIDs for a database index, look at v7 (RFC 9562) generated via a library like `uuid` v9+ — out of scope for this tool.

Common Use Cases

Distributed primary keys
Assign a UUID in the application layer before the row is inserted, so multiple services can create records concurrently without a centralised sequence generator or a round-trip to the database.
Idempotency keys for retried API calls
Attach a freshly generated UUID as an Idempotency-Key header. If the network times out and the client retries, the server recognises the duplicate and returns the original response instead of processing the request twice.
Collision-free file and object names
Name uploaded files or cloud storage objects with a UUID to eliminate name collisions across users and environments without any coordination logic.
Correlation IDs in distributed tracing
Inject a UUID into the X-Request-ID or trace-id header at the edge and propagate it through every downstream service call so all log lines for one user request can be grouped together.

Frequently Asked Questions

When should I prefer v7 over v4?

Use v7 when the IDs will be the primary key of a relational or document database — its millisecond timestamp prefix makes inserts sequential, keeps index pages hot, and makes the IDs naturally sortable by creation time. For everything else, v4 (what this tool produces) is fine and simpler. If you need v7, generate it server-side with a library like `uuid` v9+.

How likely is a v4 UUID collision?

Extremely unlikely. You would need to generate approximately 2.71 × 10^18 UUIDs (roughly 2^61) before reaching a 50% probability of a single collision. In practice this is never a concern for any real application.

Why should I not use UUIDs for short URLs or user-facing IDs?

A canonical UUID is 36 characters (32 hex + 4 hyphens). It is too long for URLs, hard to type, and visually noisy. For user-facing tokens consider a shorter random ID like nanoid or a base-62 encoded random integer.

What is the difference between v1 and v4?

v1 embeds the MAC address of the generating machine plus a high-resolution timestamp, which leaks infrastructure information. v4 is fully random with no identifying data. Modern systems should avoid v1 for privacy reasons; if you need time-ordering use v7 instead.

Are UUIDs suitable for security tokens?

A v4 UUID contains 122 bits of randomness, which is technically sufficient entropy for a non-guessable token. However, purpose-built libraries (e.g. crypto.randomBytes in Node.js) are the preferred choice for security-critical tokens such as password-reset links.

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