Every developer needs unique identifiers. Whether you are designing a database schema, generating API keys, creating test data, or tracking user sessions, you need identifiers that are guaranteed to be unique across systems and over time. The standard solution is a UUID — a Universally Unique Identifier that requires no central coordination and carries virtually zero risk of collision.
But getting a UUID should not be a chore. Installing an npm package just to generate a few IDs feels like overkill. Command-line tools like uuidgen work fine on macOS, but they are not available on Windows by default and offer no formatting options. Meanwhile, many online "free" tools bombard you with ads, require registration, or — worse — generate identifiers on their servers, creating a potential privacy risk.
That is why we built a better way. Our free online UUID Generator is a 100% client-side, zero-registration tool that runs entirely in your browser. It supports both UUID v4 (fully random) and the modern UUID v7 (time-sortable), offers bulk generation up to 1,000 IDs at once, and includes handy features like format customization and a local history log. No ads. No tracking. No server round-trips.
What Is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit label used to identify information in computer systems. The canonical textual representation is a 36-character string formatted as eight groups of hexadecimal digits separated by hyphens:
550e8400-e29b-41d4-a716-446655440000This format — 8-4-4-4-12 — is defined by IETF RFC 9562 (which obsoletes the earlier RFC 4122). The standard specifies several versions of UUID, each generated through a different algorithm. Despite the different generation methods, all versions produce identifiers from the same 128-bit address space.
The probability that a randomly generated UUID collides with another is approximately 2.71 × 10^18. In practical terms, this means you could generate a billion UUIDs every second for roughly 85 years and still have a less than 50% chance of a single collision. For all real-world applications, UUIDs can be treated as unique without any centralized registry or coordination.
UUID Version Comparison
Not all UUIDs are created equal. The RFC defines multiple versions, and choosing the right one matters for performance, privacy, and usability.
UUID v1 — Timestamp + MAC Address
UUID v1 combines the current timestamp with the MAC address of the generating machine. While this guarantees uniqueness, it has a critical flaw: it exposes the MAC address and the exact time the UUID was created. This creates a privacy risk and makes v1 unsuitable for public-facing identifiers. It is also sortable by time, but the privacy trade-off is rarely worth it.
UUID v4 — Pure Randomness
UUID v4 is the most widely used version today. It generates 122 bits of pure randomness (6 bits are reserved for version and variant identifiers). The result is completely unpredictable and privacy-safe. However, because the random bits are uniformly distributed, v4 UUIDs are not sortable by creation time. If you use them as database primary keys, they cause index fragmentation in B-tree structures because new inserts are scattered randomly across the index.
UUID v7 — Time-Sortable + Random
UUID v7, introduced in RFC 9562 in 2024, is the modern standard designed specifically to solve the problems of v4. Its structure is elegant:
- First 48 bits: Unix timestamp in milliseconds
- Remaining bits: Random entropy
This means UUID v7 values are naturally sortable by time while still containing enough randomness to guarantee uniqueness. When used as database primary keys, v7 UUIDs insert sequentially into B-tree indexes, dramatically reducing fragmentation and improving write performance. They also preserve the privacy benefits of v4 because the random suffix prevents reverse-engineering.
Quick Comparison
| Version | Structure | Sortable | Privacy-Safe | Best For |
|---|---|---|---|---|
| v1 | Timestamp + MAC | Yes | No (exposes MAC) | Legacy systems only |
| v4 | 122-bit random | No | Yes | General use, API keys, tokens |
| v7 | Timestamp + random | Yes | Yes | Database PKs, event logs, modern apps |
Our tool supports both v4 and v7, so you can choose the right version for your use case with a single click.
Common Use Cases for UUIDs
Database Primary Keys
Replacing auto-incrementing integers with UUIDs eliminates the need for a central ID generator in distributed systems. Each node can create IDs independently without coordination. UUID v7 is especially valuable here because its time-sortable nature prevents the index fragmentation that plagues v4 primary keys in high-write databases.
API Keys and Authentication Tokens
UUIDs provide an excellent source of cryptographically secure random tokens. The 122 bits of randomness in v4 (and the random component of v7) produce values that are computationally infeasible to guess. Many platforms use UUID-formatted strings for API keys, refresh tokens, and password reset links.
Session Identifiers
Web applications need a way to track user sessions across stateless HTTP requests. A UUID assigned at login and stored in a cookie provides a simple, collision-resistant session ID. Because our generator runs entirely in the browser, you can even prototype session-handling logic locally without any backend dependencies.
Test Data Generation
When building or testing applications, you often need realistic-looking data. Generating hundreds or thousands of UUIDs to populate user tables, order records, or message queues is a common task. Our bulk generation feature lets you create up to 1,000 UUIDs instantly and download them as a .txt file for import into your test suite.
Distributed Systems and Microservices
In a microservices architecture, multiple services may need to create records that reference each other. Using UUIDs means services can generate IDs independently without calling a central ID service. This reduces latency, eliminates a single point of failure, and simplifies service boundaries.
File Naming and Upload Handling
When users upload files to a shared storage system, naming collisions are inevitable if you use the original filenames. Prefixing or replacing filenames with UUIDs guarantees uniqueness. A file named report.pdf becomes 550e8400-e29b-41d4-a716-446655440000.pdf, ensuring that two users uploading files with the same name never overwrite each other.
Tool Features
Our UUID Generator is designed to be the fastest, simplest way to get the identifiers you need.
Single UUID Generation
Click the Generate button (or press Ctrl+Enter) and a new UUID appears instantly in a large, readable card. The high-contrast display makes it easy to read and transcribe when you need to paste it into a terminal, config file, or database query.
Bulk Generation
Need more than one? Enter any quantity from 1 to 1,000, hit Generate, and receive a complete list. You can copy the entire set to your clipboard or download it as a plain .txt file with one UUID per line. This is perfect for seeding test databases or generating large batches of API keys.
Version Switching
Toggle between v4 (fully random) and v7 (time-sortable) at any time. The interface clearly labels which version is active, and the generated output updates immediately. If you are building a new application, we recommend defaulting to v7 for database keys.
Format Options
Not every system accepts the standard hyphenated format. Our tool lets you switch between:
- Lowercase with hyphens:
550e8400-e29b-41d4-a716-446655440000 - Uppercase with hyphens:
550E8400-E29B-41D4-A716-446655440000 - Lowercase without hyphens:
550e8400e29b41d4a716446655440000 - Uppercase without hyphens:
550E8400E29B41D4A716446655440000
History Log
The tool keeps a running list of your last 10 generated UUIDs. Each entry has its own copy button, so you can go back and grab a previous ID without regenerating. The history is stored in your browser's session and clears when you close the tab — no persistent tracking.
Keyboard Shortcuts
Power users can press Ctrl+Enter to generate a new UUID without touching the mouse. This small efficiency gain adds up when you are generating dozens of IDs during a development session.
Privacy and Security
We believe that a tool this simple should not compromise your privacy.
All UUIDs are generated locally in your browser using the Web Crypto API's crypto.getRandomValues(). This is the same cryptographically secure random number generator that powers TLS connections and other browser security features. No data is ever sent to our servers.
We do not use cookies, analytics scripts, or tracking pixels. We do not know how many UUIDs you generate, what versions you prefer, or even that you visited the page. The tool is a static single-page application hosted on Cloudflare Pages, and once loaded, it functions entirely offline. If you have already visited the page, you can disconnect from the internet and continue generating UUIDs without interruption.
Compare this to many other "free" online tools that generate identifiers server-side. In those cases, the service provider has a record of every UUID you create. If you are generating API keys, session tokens, or any identifier that grants access to a system, server-side generation introduces an unnecessary trust assumption. Our client-side approach removes that risk entirely.
Online Tool vs. Command Line vs. Programming Libraries
There are three common ways to generate UUIDs. Each has its place.
| Method | Setup Required | Cross-Platform | Bulk Support | Format Options | Best For |
|---|---|---|---|---|---|
| Our Online Generator | None | Yes (any browser) | Up to 1,000 | Full control | Quick tasks, all platforms, bulk needs |
Command Line (uuidgen) | Pre-installed on macOS; Linux via uuid-runtime | No (Windows not included) | No | None | Terminal-heavy workflows on Unix systems |
Programming Libraries (uuid npm package, Python uuid module) | Requires project environment | Yes (within the runtime) | Via scripting | Via code | Automated pipelines, application code |
Use the online tool when you need a UUID right now without installing anything. It is the fastest path from "I need an ID" to "here it is."
Use the command line when you are already in a terminal and only need a single UUID on a Unix system. It is fast but limited.
Use a programming library when UUID generation is part of an automated workflow, a test suite, or application logic. It offers maximum flexibility but requires setup.
How to Use the UUID Generator: Step by Step
- Open the tool: Navigate to uuid-generator-eyf.pages.dev. The page loads instantly with no registration required.
- Choose your version: Click the v4 or v7 toggle. If you are unsure, start with v7 for database keys and v4 for general random tokens.
- Generate: Click the Generate button or press Ctrl+Enter. Your UUID appears in the display card.
- Copy: Click the copy icon next to the UUID to save it to your clipboard. A brief confirmation tells you the copy succeeded.
- Bulk generate: Switch to the Bulk tab, enter a quantity (1–1,000), and click Generate. Copy the full list or download it as a
.txtfile. - Review history: Check the History section below the generator to see your last 10 UUIDs. Click any entry to copy it individually.
That is it. No accounts, no ads, no waiting.
Frequently Asked Questions
Is this UUID generator free to use?
Yes. The tool is completely free with no usage limits, no registration, and no premium tier. Generate as many UUIDs as you need, as often as you need them.
Does it work offline?
Yes. Once the page has loaded, it functions entirely in your browser without any server connection. You can disconnect from the internet and continue generating UUIDs. This also makes it usable in restricted network environments.
Are the UUIDs generated securely?
Yes. We use the browser's native crypto.getRandomValues() API, which provides cryptographically secure random numbers suitable for security-sensitive applications like session tokens and API keys.
What is the difference between UUID v4 and v7?
UUID v4 is fully random. It is privacy-safe and unpredictable, but its random distribution makes it unsortable. UUID v7 embeds a Unix timestamp in the first 48 bits followed by random data. This makes v7 sortable by creation time while retaining privacy and uniqueness guarantees. v7 is the recommended choice for database primary keys.
How many UUIDs can I generate at once?
You can generate up to 1,000 UUIDs in a single bulk operation. The output can be copied to your clipboard or downloaded as a .txt file.
Can I use generated UUIDs for commercial projects?
Absolutely. UUIDs are standard, open identifiers. There are no licensing restrictions on their use. Generate them for personal, commercial, or open-source projects without restriction.
Where are my generated UUIDs stored?
They are not stored on any server. The history log visible on the page is kept only in your browser's memory for the current session and disappears when you close the tab. For maximum privacy, copy your UUIDs and close the page when done.
Why should I use UUID v7 over v4?
If you are using UUIDs as database primary keys, v7 is superior because its time-sortable structure prevents index fragmentation. This leads to better write performance and more efficient storage. For API keys, tokens, or other non-sortable use cases, v4 remains an excellent choice.
Can I generate UUIDs without dashes?
Yes. The tool includes format options that let you toggle hyphens on or off and switch between uppercase and lowercase. This is useful when integrating with systems that expect a compact 32-character string.
Is there a risk of duplicate UUIDs?
The probability of generating a duplicate UUID is approximately 2.71 × 10^18. For context, this is lower than the odds of being struck by lightning multiple times in the same year. In practice, duplicates are not a concern.
Do you offer other developer tools?
Yes. Explore our full tools directory for more free utilities, including the Password Generator, Hash Generator, Timestamp Converter, Online Calculator, and Base64 Tool.
Start Generating UUIDs Now
A good developer tool gets out of the way and lets you work. Our free online UUID Generator does exactly that: no setup, no accounts, no distractions. Just clean, secure, standards-compliant UUIDs generated instantly in your browser — with full support for the modern v7 standard.
Whether you need a single ID for a database record or a thousand for a test suite, the tool is ready.
While you are here, check out our other free developer tools: Password Generator, Hash Generator, Timestamp Converter, Online Calculator, and Base64 Tool. Or browse the complete tools directory to see everything we offer.