UUID Generator for Random v4 and Time-Ordered v7 Identifiers

What Is a UUID?

A UUID is a 128-bit identifier used to label records, objects, sessions, API resources, database rows, files, and other items without relying on a central numbering service. UUIDs are also commonly called GUIDs.

A standard textual UUID contains 32 hexadecimal digits separated into five groups by hyphens.

The UUID generator on this page supports UUID v4 and UUID v7, the two versions most useful for general random IDs and newer time-ordered IDs.

UUID v4 vs UUID v7

RFC 9562 defines both versions. UUID v4 is based on random data, while UUID v7 places a Unix timestamp in the most significant 48 bits and uses random data for the remaining variable bits.

When to Use UUID v4

UUID v4 is a strong default when you simply need a random identifier that can be generated independently across different systems.

It is widely used for API resources, application records, object IDs, temporary test data, and distributed systems where central coordination would be inconvenient.

When to Use UUID v7

UUID v7 is useful when the identifier should retain UUID compatibility while also sorting roughly by creation time.

That can be useful in databases, logs, event streams, and systems where newly created records are frequently inserted and later sorted by time.

RFC 9562 recommends UUID v7 over older time-based versions for many new applications that need time ordering.

How UUID v4 Is Generated

UUID v4 starts with random or pseudorandom data. Specific bits are then replaced to mark the UUID version and RFC variant.

UtilityDocks uses the browser Web Crypto interface rather than Math.random(). Web Crypto provides access to a cryptographically strong random source in supported browsers.

How UUID v7 Is Structured

UUID v7 begins with the Unix timestamp measured in milliseconds. The timestamp occupies the first 48 bits, while the remaining variable bits provide randomness together with the required version and variant fields.

Because the timestamp is placed at the start, UUID v7 values generated later generally sort after earlier values when compared in their standard binary or canonical order.

UUID vs GUID

UUID and GUID are often used interchangeably. RFC 9562 explicitly notes that UUIDs are also known as Globally Unique Identifiers, or GUIDs.

In everyday development, a GUID generator usually refers to the same 128-bit identifier format. Microsoft platforms commonly use the term GUID, while many cross-platform tools and standards use UUID.

Understanding UUID Formatting

The standard canonical representation uses lowercase or uppercase hexadecimal characters with hyphens.

The case of hexadecimal letters does not change the underlying UUID value. Some systems, however, expect a particular display format, so the tool lets you switch case, hyphens, and braces.

Can Two UUIDs Be the Same?

UUIDs are designed to make collisions extremely unlikely, but they should not be described as mathematically impossible.

UUID v4 has 122 random bits after reserving the required version and variant bits. That creates a very large possible space, which is why v4 is widely used in distributed applications.

Applications that require an absolute guarantee of uniqueness may still enforce a unique database constraint and handle the rare possibility of a duplicate.

Why Generate Multiple UUIDs at Once?

Bulk generation is useful when creating fixtures, seed data, test records, sample API objects, or batches of identifiers for development work.

The tool can generate up to 1,000 UUIDs at once. You can copy the complete list or download it as a text file.

UUIDs in Databases and APIs

UUIDs work well when records need identifiers that can be created before they reach a central database. Separate services can generate IDs without first requesting the next number from one shared sequence.

UUID v4 is simple and widely supported. UUID v7 can be attractive when a database or event system benefits from identifiers that are naturally ordered by creation time.

The best version still depends on the database engine, indexing strategy, application requirements, and how the identifier is exposed.

Are UUIDs Secure?

A UUID can be difficult to guess, especially when generated from strong random data, but UUIDs are not an authentication mechanism.

Do not use the secrecy of a UUID as the only protection for private records. Access control should be handled separately with proper authentication and authorization.

UUID Generator FAQs

Standards and Generation Method

Technical details reviewed September 16, 2026.

The page follows the current UUID specification in RFC 9562. UUID v4 uses browser-generated random bytes with the required version and variant bits. UUID v7 uses the Unix timestamp in milliseconds plus random bits.

• RFC Editor: RFC 9562, Universally Unique IDentifiers (UUIDs)
• MDN Web Docs: Crypto and Crypto.randomUUID()