UUID v4 (GUID) Generator

UUID v4/GUID generator: what this page creates and how to use it

This browser tool creates UUID version 4 values, which many teams also call GUIDs. Each result is a 128-bit identifier formatted as five hyphenated groups of hexadecimal characters, so it can be pasted directly into code, test fixtures, temporary records, or log annotations without extra cleanup.

Privacy note: generation happens in your browser, and the IDs are produced locally rather than being sent to a server by this page's generator logic.

How to use this UUID generator

1. Enter how many UUIDs you need, from 1 to 10.
2. Select Generate UUIDs to fill the output box with one ID per line.
3. Select Copy to move the full batch to your clipboard, or Clear if you want a fresh start.

What a UUID v4 looks like and how the pieces fit

A UUID is a standardized identifier defined by RFC 4122. The common 8-4-4-4-12 layout makes it easy to scan in logs, database rows, and configuration files:

xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx

• M is the version; for a v4 UUID this position is always 4.
• N is the variant; for RFC 4122 UUIDs, the high bits correspond to 8, 9, a, or b in that position.

Why UUID v4 uses randomness and why the ID space is so large

UUID v4 uses random bits for most of its value. After the version and variant bits are fixed, 122 bits remain unpredictable, so the total number of possible v4 UUIDs is:

That enormous space is the reason UUID v4 is attractive for distributed systems, browser-side drafting, and any workflow where separate clients should be able to mint IDs without coordinating with each other. The result is best described as probabilistically unique: collisions are so unlikely that they are usually a non-issue, but they are still not mathematically impossible.

When teams choose UUIDs, and when another identifier is a better fit

UUIDs are popular because they can be created without a central sequence and are difficult to predict compared with incrementing numbers. Common places to use them include:

• Database keys in distributed systems, where multiple services may create records independently and should not block on a shared counter.
• Client-generated IDs for offline-first apps, so a draft can receive an identifier before it is synced to a server.
• Trace and event IDs in logging pipelines, where a short-lived but unique tag is useful for following activity across components.
• File or object names when predictable names could clash or reveal unnecessary information.

They are not ideal everywhere. UUIDs take more space than simple integers, can be less friendly to some database indexes, and do not encode creation order in version 4. If your application needs sortable identifiers, consider ULIDs or UUID v7 where your platform supports them.

Worked example: generating three UUIDs for draft records

Imagine you are building a local draft list before a user saves anything to the server.

1. Set Number of UUIDs to 3.
2. Select Generate UUIDs.
3. Use the resulting lines to tag three draft rows, temporary objects, or test entries.

The specific values will be different every time you click Generate, but the workflow stays the same: one UUID per line, ready to copy, paste, or attach to a record while the item is still being edited.

UUID versions at a glance

Interpreting and validating UUID v4 output

This generator writes lowercase hexadecimal characters with hyphens, one UUID per line. Many systems also accept uppercase text, but a strict validator may insist on the exact RFC 4122 v4 pattern shown below.

^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$

If another system wants braces, uppercase letters, or a hyphen-free format, transform the copied string after generation. This page only produces the canonical hyphenated form, so any alternate formatting must happen in your application or editor.

UUID v4 limitations and assumptions

• UUID version: This tool generates version 4 (random) UUIDs only, so it does not create time-based or name-based identifiers.
• Randomness source: It prefers crypto.randomUUID() when available. If that API is not present, it falls back to crypto.getRandomValues(), and older browsers may use a non-cryptographic fallback.
• Not a secret: A UUID is an identifier, not a password or API key. Use dedicated secret generation for anything that protects access.
• Probabilistic uniqueness: Collisions are extremely unlikely, but critical systems should still enforce uniqueness where that matters, such as a database unique constraint.
• Batch size: You can generate between 1 and 10 UUIDs per click so the output stays easy to read and copy.
• Formatting: Output is lowercase and hyphenated. If your target system expects another style, you will need to adapt it after copying.

UUID v4 generator FAQ

If you are comparing UUID v4 output with the terms you see in logs, database schemas, or Microsoft documentation, these answers cover the most common questions about this generator.

Is GUID just another name for UUID?

Yes. In everyday developer usage, GUID is Microsoft terminology for a UUID, and the values you see in either format usually follow the same 128-bit structure.

How does this UUID generator create the IDs?

The page runs entirely in your browser. It uses crypto.randomUUID() when possible, falls back to crypto.getRandomValues() if needed, and only uses a Math.random-based method in older environments that lack the newer APIs. The result is always a batch of one UUID per line.

Can I use a UUID as a secret or API key?

No. UUIDs are meant for identification, not authentication. They are fine for record IDs, draft references, file names, and log tags, but anything that gates access should be generated and stored as a real secret.

Why does the generator stop at 10 UUIDs?

That limit keeps the page responsive and the output manageable when you are copying IDs by hand. If you need a larger batch, generate multiple rounds and combine the lines yourself.

How this UUID generator decides what to output

There is no numeric estimate formula on this page. The only setting you choose is the batch size, and the generator uses that count to create the same number of independent UUID v4 values.

After generation, the page formats each ID with hyphens and places the results one per line. If you are checking the output, the important details are the version nibble, the variant position, and whether your downstream system wants the canonical lowercase form or a transformed version.