---
title: "UUID Generator | Method Calculator"
description: "Generate random version 4 UUIDs (GUIDs) one at a time or in bulk, in lowercase or uppercase, with or without hyphens and braces, and copy them in one click."
canonical_url: "https://methodcalculator.com/uuid-generator"
meta:
  "og:description": "Generate random version 4 UUIDs (GUIDs) one at a time or in bulk, in lowercase or uppercase, with or without hyphens and braces, and copy them in one click."
  "og:image": "https://methodcalculator.com/_og/s/o_da55c1abc5a92962.png"
  "og:image:height": "600"
  "og:image:type": image/png
  "og:image:width": "1200"
  "og:title": "UUID Generator – Free Online Tool"
  "twitter:image": "https://methodcalculator.com/_og/s/o_da55c1abc5a92962.png"
---

> Index of every page on this site: [llms.txt](https://methodcalculator.com/llms.txt)

# **UUID Generator**

Choose how many UUIDs you need and the formatting you want, and fresh version 4 identifiers appear instantly. Click Generate for a new batch or Copy all to put them on your clipboard.

## **5 UUIDs**

Generating…

<dl>

<dt>Version</dt>
<dd>4 (random)</dd>

<dt>Variant</dt>
<dd>RFC 4122 / 9562</dd>

<dt>Random bits per UUID</dt>
<dd>122</dd>

<dt>Possible values</dt>
<dd>**2¹²² ≈ 5.3 × 10³⁶**</dd></dl>

## What is a UUID?

A UUID (universally unique identifier), also called a GUID in the Microsoft world, is a 128-bit number written as 32 hexadecimal digits in five groups separated by hyphens, for example `9b2c4f1e-3a7d-4c58-9e21-0f6b8d5a7c3e`. Its purpose is to let independent systems create identifiers at the same time without a central authority and still never clash. The format is defined in RFC 4122, revised in 2024 as RFC 9562, and is supported natively by every major database, programming language and operating system.

## The structure of a version 4 UUID

A version 4 UUID is almost entirely random. Of its 128 bits, four encode the version number and two encode the variant (the layout family); the remaining **122 bits are random**. In the text form the fixed bits are easy to spot:

`xxxxxxxx-xxxx-**4**xxx-**y**xxx-xxxxxxxxxxxx`

| Group | Hex digits | Bits | Contents |
| --- | --- | --- | --- |
| 1 | 8 | 32 | Random |
| 2 | 4 | 16 | Random |
| 3 | 4 | 16 | First digit is always 4 (the version), then 12 random bits |
| 4 | 4 | 16 | First digit is 8, 9, a or b (the variant bits 10), then 14 random bits |
| 5 | 12 | 48 | Random |

**Example:** the generator asks the browser for 16 random bytes, then forces byte 7 to start with the bits 0100 (hex 4) and byte 9 to start with 10. With 122 free bits there are 2¹²² ≈ **5.3 × 10³⁶** distinct UUIDs: 5.3 undecillion, or about 5 trillion trillion trillion.

## How likely is a collision?

The birthday problem gives the answer. The number of random UUIDs you can generate before the chance of any duplicate reaches 50% is roughly the square root of 2 × ln 2 × 2¹²², about **2.7 × 10¹⁸**. Generating one billion UUIDs every second, it would take around 86 years to get there. For a more realistic 10¹² identifiers (a trillion rows), the probability of even one duplicate is about n² ÷ (2 × 2¹²²) ≈ 10⁻¹³. That is why applications treat v4 UUIDs as unique without checking.

## How to use this generator

1. Enter how many UUIDs you need, up to 100 per batch.
2. Tick Uppercase, Remove hyphens or Wrap in braces to match the format your system expects. These options reformat the current batch without regenerating it.
3. Click Copy all (or Copy for a single ID) to put the list on your clipboard, one UUID per line.
4. Click Generate new for a fresh batch. Previous batches are not stored anywhere.

## UUID versions compared

| Version | Built from | Use it when |
| --- | --- | --- |
| v1 | Timestamp + MAC address + clock sequence | Rarely today; it reveals when and on which machine the ID was made |
| v4 | 122 random bits | You need an unpredictable ID with no coordination (the default choice) |
| v5 | SHA-1 hash of a namespace and a name | The same input must always give the same UUID |
| v7 | Unix timestamp in milliseconds + random bits | Database primary keys, where time-ordered IDs index and insert faster |

## Where UUIDs are used, and tips

- **Database keys and API resources:** records can be created on any server or offline device and merged later without renumbering.
- **File and session names:** uploads, temporary files and job IDs that must not collide.
- **Correlation IDs** that follow a request through logs across several services.
- **Prefer lowercase with hyphens** for storage and comparison; many systems treat case as insignificant, but some string comparisons do not.
- **Random is not secret.** IDs appear in URLs and logs, so never rely on a UUID as the only protection for private data. For keys and tokens use the [password generator](https://methodcalculator.com/password-generator); for plain numbers use the [random number generator](https://methodcalculator.com/random-number-generator).

## **Frequently asked questions **

### **Are the UUIDs generated here unique?**

Each one contains 122 random bits from the browser's cryptographically secure generator, giving 5.3 × 10³⁶ possible values. You would need to generate about 2.7 quintillion UUIDs before there was even a 50% chance that any two matched, so for practical purposes they are unique without any coordination between systems.

### **What is the difference between a UUID and a GUID?**

Nothing in practice. GUID (globally unique identifier) is Microsoft's name for the same 128-bit format defined in RFC 4122 (now RFC 9562). Microsoft tools often display GUIDs in uppercase and wrapped in braces, which the formatting options here reproduce.

### **Which UUID version should I use?**

Version 4 is the right default when you just need an unpredictable unique ID. Choose version 7 if the IDs will be primary keys in a database that benefits from time-ordered inserts. Version 1 embeds the time and a MAC address, which leaks information and is rarely wanted today.

### **Can I use a UUID as a password or secret token?**

A v4 UUID from a secure generator has 122 bits of entropy, more than enough, but UUIDs are designed as identifiers and tend to end up in URLs, logs and error messages. For secrets, generate a dedicated random string with the password generator and keep it out of identifiers.

### **Is a UUID with no hyphens still valid?**

The 32-character hex form is widely accepted (for example by Python's uuid module and most databases), but the canonical representation in the standard uses hyphens. Use the hyphenated lowercase form unless the system you are feeding specifically asks for something else.

## **Related calculators **

- [**Password Generator**](https://methodcalculator.com/password-generator)
- [**Random Number Generator**](https://methodcalculator.com/random-number-generator)
- [**QR Code Generator**](https://methodcalculator.com/qr-code-generator)
- [**Lorem Ipsum Generator**](https://methodcalculator.com/lorem-ipsum-generator)

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```

## Sitemap

See the full [sitemap](https://methodcalculator.com/sitemap.md) for all pages.