UUID Generator — Bulk v4 Generation, No-Hyphens & Uppercase Formats

Generate any number of UUID v4 (random) identifiers in bulk, right in your browser. One click converts to standard, uppercase, no-hyphens, braces, or URN format, ready to copy. Free, no sign-up required.

Last updated: 2026-09-06

UUID versions at a glance

Version	Based on	Description
UUID v1	Timestamp + MAC address	Generated from the creation time and the network card's MAC address. Can reveal the generating device, so it has raised privacy concerns and is rarely chosen for new systems today.
UUID v3	Namespace + MD5 hash	Generated by hashing a namespace and a name string with MD5. Deterministic — the same input always produces the same UUID. v5 is now preferred for new use due to MD5's known collision weaknesses.
UUID v4	Fully random	Generated from a cryptographically secure random source. Reveals no information about its origin and is simple to implement, making it the most widely used variant. This is the format this tool generates.
UUID v5	Namespace + SHA-1 hash	Same namespace-based approach as v3, but uses SHA-1. Recommended when you need deterministic generation — reproducing the same ID from the same data every time.
UUID v6	Reordered timestamp + random	Standardized in RFC 9562 (2024). Reorders v1's timestamp fields so lexicographic byte order matches chronological order, improving database index efficiency.
UUID v7	Unix timestamp + random	Standardized in RFC 9562 (2024). Leads with a millisecond-precision Unix timestamp, so IDs sort in creation order. Increasingly adopted as a v4 replacement in new projects.

What a UUID is and how these are made

A UUID (Universally Unique Identifier) is a 128-bit identifier designed never to collide anywhere in the world, used for database primary keys, API request identifiers and similar purposes. Its appeal is that no central server has to hand out sequential numbers: every machine can mint one independently and, in practice, they will not clash.

This tool generates version 4 UUIDs — entirely random ones — inside your browser using the Web Crypto API. Nothing is sent to a server. Generate as many as you need in one go, then switch with a single click between the standard form, hyphenless, uppercase, brace-wrapped and URN notation, and copy the result.

How to generate UUIDs

Set how many you need Enter the number of identifiers. You can ask for a large batch when you are preparing test data or seed data.
Choose the output format Besides the standard lowercase, hyphenated form, you can select hyphenless, uppercase, brace-wrapped or URN notation to match what your target expects.
Generate and copy Pressing generate lists the results. Use "copy all" or the individual copy buttons to place them on the clipboard.

Tips for getting more out of it

Every UUID is generated entirely in your browser via the Web Crypto API — nothing is ever sent to toolbase.cc's servers.
UUID v4 is the go-to choice whenever you need uniqueness without sequential, guessable IDs — database primary keys, API request IDs, and more.
Since 122 of UUID v4's 128 bits are random, the odds of a collision are astronomically small — you'd need to generate about 2.7×10¹⁸ of them before the collision probability even reaches roughly 50%.
The "no hyphens" format is handy for URL path segments or filenames. The "braces" format matches the GUID notation used in Windows COM/registry contexts.
Bump up the count and use "Copy all" to quickly generate seed data or test fixtures in bulk.

When generating UUIDs is useful

Designing database primary keys

For tables where you do not want sequential keys, or do not want the origin to be guessable, a version 4 UUID gives you a key you need not worry about colliding.

Request and trace identifiers in an API

When you attach a unique identifier to each request so that logs can be followed during debugging, you can produce as many as you need at once.

Preparing test and seed data

When loading initial data into a development environment, generate a batch of non-colliding identifiers to the exact count you need and paste them straight in.

File names and short-lived tokens

The hyphenless form works well as a temporary name for an uploaded file, or as a token that is hard to guess.

Terms used with UUIDs

UUID v4: A UUID generated from a cryptographically secure random source, carrying no information about where it came from. Simple to implement and sound from a privacy standpoint, it is by far the most widely used version.
GUID: The name Microsoft gave to UUIDs in its own implementations. It refers to the same compatible 128-bit identifier and is often written wrapped in braces.
Web Crypto API: The set of cryptography-related JavaScript interfaces built into browsers. This tool uses it to generate version 4 UUIDs entirely in the browser, with nothing sent to a server.
URN notation: A UUID written with the prefix urn:uuid:. It is used when embedding a UUID as an identifier inside specifications that expect a URN, such as XML or RDF.
UUID v7: Standardised in RFC 9562 in 2024, this version begins with a Unix timestamp. Because the values sort in generation order, it is increasingly chosen over v4 in new projects where efficient database insertion matters.

Frequently asked questions

Not impossible in theory, but with 122 bits of randomness, UUID v4's collision risk is negligible for any practical purpose. Even generating a billion UUIDs per second for a hundred years straight would only bring the odds of a single collision to around 50%.

Yes, they're essentially the same concept. GUID (Globally Unique Identifier) is Microsoft's name for its own implementation, and it's compatible with the 128-bit UUID format. The braces notation {xxxxxxxx-xxxx-...} is the common GUID style used in Windows COM and the registry.

Because UUID v4 is random, it tends to produce larger indexes and slower inserts than sequential integers (AUTO_INCREMENT). If you need inserts to stay sorted by creation time, consider UUID v7 (which embeds a timestamp) or ULID as an alternative.

If all you need is uniqueness, UUID v4 is the simplest and safest choice. Use v5 when you need to reproduce the same ID from the same input every time. For new projects that care about sort order or database insert efficiency, v7 is a strong option. v1 and v3 see little new adoption today.

Side Note — Why 128 Bits?

The UUID was devised in the 1980s by Apollo Computer for distributed systems, and later standardized by the OSF (Open Software Foundation) as part of DCE (Distributed Computing Environment). Today's specification lives in IETF RFC 4122 (2005), with an expanded RFC 9562 published in 2024.

128 bits might look excessive, but that length is what lets multiple servers or devices mint IDs completely independently, with zero coordination, while still avoiding collisions in practice. A central ID-issuing server that hands out sequential numbers avoids that randomness, but creates a single point of failure and requires a round trip for every ID. UUIDs eliminate that coordination cost entirely, trading it for enough randomness that the collision probability becomes negligible.

That randomness is also UUID v4's Achilles' heel: inserting random values into a B-tree style database index scatters the insert points, triggering frequent page splits and hurting performance. UUID v7 was devised to fix exactly this — by leading with a Unix timestamp, it stays sortable by creation time while keeping enough randomness to avoid predictability, giving inserts much better locality.

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