Question 1

What is a UUID?

Accepted Answer

A UUID (Universally Unique Identifier) is a 128-bit identifier standardized in RFC 4122 (and updated in RFC 9562). It is represented as 32 hexadecimal digits in five groups separated by hyphens, like 550e8400-e29b-41d4-a716-446655440000. The total number of possible UUIDs is 2^128 (about 3.4 × 10^38), which is so vast that randomly generated UUIDs are practically guaranteed to be unique without any central coordination.

Question 2

What UUID versions are supported?

Accepted Answer

This tool supports three versions: UUID v4 (random — the most common, using cryptographically secure random numbers), UUID v7 (timestamp-sortable — combines a Unix timestamp with random bits for database-friendly chronological ordering), and UUID v1 (time-based — derived from the Gregorian timestamp and a random node identifier). Each version has different properties; v4 is the safe default for most use cases.

Question 3

Are generated UUIDs truly random?

Accepted Answer

For v4 and v7 UUIDs, yes. This tool uses the Web Crypto API (crypto.getRandomValues), which provides cryptographically secure pseudo-random numbers (CSPRNG) supplied by the browser. This is the same randomness source used for encryption keys and security tokens. If the Web Crypto API is unavailable (e.g., in a very old browser), it falls back to Math.random, which is less secure but still produces well-distributed values. UUID v1 is not fully random — its value is derived from the current timestamp and a random node identifier.

Question 4

What's the difference between UUID v4 and v7?

Accepted Answer

UUID v4 is purely random — all 122 variable bits are filled with random data, so v4 UUIDs have no inherent ordering. UUID v7, introduced in RFC 9562, uses a 48-bit Unix timestamp (millisecond precision) as the most significant bits, with 74 bits of randomness for the rest. This means v7 UUIDs sort chronologically by creation time, making them much better for database indexes — sequential inserts reduce B-tree fragmentation and page splits. Use v4 when you need pure randomness; use v7 when you need uniqueness plus time-orderability, such as for database primary keys or event logs.

Question 5

Can I generate multiple UUIDs at once?

Accepted Answer

Yes. You can generate anywhere from 1 to 10,000 UUIDs in a single batch. Use the quantity dropdown to pick a preset (1, 5, 10, 100, or 1000) or choose "Custom" to enter any number up to 10,000. All UUIDs in a batch are guaranteed unique — the tool uses a Set internally to deduplicate, and the UUID space is large enough that collisions essentially never happen for practical counts.

Question 6

What's the maximum number I can generate?

Accepted Answer

You can generate up to 10,000 UUIDs at once. This limit ensures the browser remains responsive — generating UUIDs is fast, but rendering 10,000 rows in the DOM takes a moment. For batches over 20, the output switches to a compact textarea view for better performance. If you need more than 10,000, simply run the generator multiple times and download each batch.

Question 7

Are UUIDs guaranteed to be unique?

Accepted Answer

In practice, yes. The probability of a collision between two random v4 UUIDs is 1 in 2^122 per pair. Even after generating 103 trillion UUIDs, the chance of a single collision is less than one in a billion. For v7 UUIDs, the timestamp prefix further reduces collision risk because UUIDs generated at different times cannot collide (only the 74 random bits vary within the same millisecond). For any real-world application — even systems generating millions of UUIDs per day — you can safely treat them as globally unique.

Question 8

Does it work offline?

Accepted Answer

Yes. The UUID Generator runs entirely in your browser using JavaScript. No network request is made during generation — all randomness comes from your browser's built-in crypto module. Once the page is loaded, you can disconnect from the internet and continue generating UUIDs. This also means your UUIDs are never sent to any server, ensuring complete privacy.

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UUID Generator

What is UUID Generator?

How to Use UUID Generator

UUID Versions Explained

UUID v1 — Time-Based

UUID v4 — Random

UUID v7 — Timestamp-Sortable

Features

Frequently Asked Questions