Question 1

What is a UUID?

Accepted Answer

A UUID (Universally Unique Identifier) is a 128-bit identifier standardized by RFC 9562. UUIDs are used to uniquely identify resources in distributed systems without central coordination. They are typically represented as 32 hexadecimal digits in the format 8-4-4-4-12.

Question 2

What is the difference between UUID v4 and UUID v7?

Accepted Answer

UUID v4 is generated from completely random data, making it unpredictable but unordered. UUID v7 embeds a Unix timestamp in the first 48 bits followed by random data, making it time-sortable and ideal for database primary keys.

Question 3

When should I use UUID v7 instead of UUID v4?

Accepted Answer

Use UUID v7 when you need time-sortable identifiers, such as database primary keys. The embedded timestamp ensures natural chronological ordering, improving index performance in B-tree databases. Use UUID v4 when ordering doesn't matter.

Question 4

What is a ULID?

Accepted Answer

A ULID (Universally Unique Lexicographically Sortable Identifier) is a 128-bit identifier encoded in Crockford's Base32. Like UUID v7, it includes a timestamp component for sortability, but uses a more compact 26-character representation.

Question 5

Are UUIDs truly unique?

Accepted Answer

While not mathematically guaranteed to be unique, the probability of collision for UUID v4 is astronomically low — about 1 in 2^122 (5.3 × 10^36). For practical purposes, UUIDs can be treated as globally unique.

Question 6

Can I extract a timestamp from a UUID?

Accepted Answer

Only from time-based UUIDs. UUID v7 stores a Unix millisecond timestamp in the first 48 bits. UUID v1 also contains a timestamp but in a different format. UUID v4 is purely random and contains no timestamp.

Question 7

What is the difference between UUID and GUID?

Accepted Answer

UUID and GUID (Globally Unique Identifier) are essentially the same thing. GUID is the term used primarily in Microsoft ecosystems, while UUID is the standard term used in RFC specifications and most other platforms.

Question 8

How do I validate a UUID?

Accepted Answer

A valid UUID matches the pattern xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx where x is a hex digit, M indicates the version (1-7), and the top bits of N indicate the variant. Our validator checks format, version, and variant automatically.

Question 9

Can I generate UUIDs in bulk?

Accepted Answer

Yes! This tool supports bulk generation of up to 100 UUIDs at once. Choose your preferred version (v4, v7, or ULID), set the count, and click Generate. You can copy all results with a single click.

Question 10

Is it safe to use online UUID generators?

Accepted Answer

Our UUID generator runs entirely in your browser using the Web Crypto API (crypto.randomUUID and crypto.getRandomValues). No UUIDs are sent to any server, making it completely safe and private.

UUID Generator

Generated UUIDs

UUID Versions and When to Use Each

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