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UUID Generator

Generate cryptographically secure UUIDs in multiple versions. Generate one or many at once and copy to clipboard.

UUID v4 - Randomly generated using cryptographically secure random bytes. The most widely used UUID version. No information about when or where it was generated is embedded.

About UUID Generator — UUID Generator Online

A UUID (Universally Unique Identifier) is a 128-bit label used to uniquely identify objects in computer systems. This UUID generator online uses your browser's crypto.getRandomValues() API — the same cryptographic source used by operating systems — so every UUID produced is truly random and statistically guaranteed to be unique across all space and time. Developers, database administrators, architects, and QA engineers rely on UUID generators daily for primary keys, correlation IDs, session tokens, and idempotency keys.

UUID generation is a fundamental task in modern software development. Whether you're bootstrapping a new microservice that needs globally unique record identifiers, seeding a test database with thousands of rows, or implementing an idempotent API endpoint that detects duplicate requests, a fast and reliable UUID generator online saves you from writing a one-off script. This tool supports four UUID versions — v4, v1, v7, and v5 — so you can pick the right format for your exact use case without switching between tools.

How to Use the UUID Generator

  1. Select a UUID Version using the tabs at the top: v4 (random) is the default and covers most use cases.
  2. Set the Count field to the number of UUIDs you want — anywhere from 1 to 100 at a time.
  3. Toggle Uppercase if your database or system requires uppercase hex characters.
  4. Toggle No hyphens if you need the compact 32-character format without dashes.
  5. Click Generate — UUIDs appear instantly. Click any individual UUID to copy it, or use Copy All to grab the entire list, or Download .txt to save them as a file.

UUID Versions Explained

Choosing the right UUID version depends on your application's requirements around randomness, sortability, and determinism. Here is a breakdown of each version this tool supports.

  • UUID v4 (Random): The most widely used version. 122 of its 128 bits are cryptographically random, with the remaining bits encoding the version and variant. No metadata about when or where it was generated is embedded, making it ideal for database primary keys, session tokens, API keys, and anywhere you need an opaque, unique value.
  • UUID v1 (Time-based): Encodes a 60-bit timestamp (100-nanosecond intervals since October 1582) plus a random node identifier. UUIDs generated close together are lexicographically similar, which can cause index clustering in some databases. Useful when you need to reconstruct rough generation order from the UUID itself.
  • UUID v7 (Time-ordered): The modern replacement for v1, standardized in RFC 9562. The first 48 bits are a Unix millisecond timestamp, making v7 UUIDs naturally sortable chronologically. This is now the recommended choice for database primary keys because it improves B-tree index performance — new records are always appended at the end of the index rather than inserted at random positions.

Tips for Getting the Best Results

UUID generation is simple, but choosing the right options for your context makes integration smoother and avoids compatibility issues downstream.

  • Prefer v4 for general-purpose unique IDs: Unless you have a specific reason to use another version, v4 is the safest default. It has no embedded metadata that could leak information about generation time or location, and every major database engine, ORM, and API framework understands the v4 format natively.
  • Use v7 for database primary keys at scale: Randomly ordered UUIDs (v4) cause page splits in B-tree indexes as rows are inserted — at high volume, this degrades write performance significantly. UUID v7 inserts in timestamp order, keeping the index tidy and maintaining predictable write throughput. If you're on PostgreSQL 17+, MySQL 8+, or a modern ORM, v7 is strongly preferred for auto-generated primary keys.
  • Use v5 for stable derived identifiers: If you need a UUID that reliably maps to a known string — for example, a canonical UUID for a product SKU or a user's email address — use v5 with a fixed namespace. The same namespace + name always produces the same UUID, so you can recreate it deterministically without storing the UUID itself.
  • Generate in bulk for seeding and testing: Set Count to 50 or 100 and click Download .txt to get a file of unique UUIDs. Paste them into SQL seed scripts, CSV import files, or test fixtures. This is faster than generating one at a time and ensures every UUID in the batch is unique.
  • Check your system's case requirements before copying: Most systems accept lowercase UUIDs, but some legacy databases, stored procedures, or legacy APIs expect uppercase. Toggle Uppercase before generating to avoid case mismatch errors during import.

Why Use a UUID Generator Online

A browser-based UUID generator online requires no installation, no runtime dependencies, and no account. You don't need Node.js, Python, or any CLI tool — just open the page and generate. Because all generation runs in your browser using the Web Crypto API, nothing is ever sent to a server. Your UUIDs are generated locally and exist only in your browser session, making this safe to use even in environments with strict data-handling policies.

This tool is particularly useful for backend developers who need UUIDs during rapid prototyping, database administrators seeding tables with test data, frontend developers mocking API responses, and QA engineers who need unique identifiers for test records. The bulk generation and download features make it practical for large-scale seeding tasks that would otherwise require a custom script.

Frequently Asked Questions about UUID Generator

Theoretically yes, but practically impossible. A UUID v4 has 2¹²² possible values — approximately 5.3 × 10³⁶. If you generated one billion UUIDs per second for the entire age of the universe, the probability of a single collision would still be astronomically small. For all practical purposes, you can treat every generated UUID as globally unique and safe to use as a primary key without a uniqueness check.
GUID (Globally Unique Identifier) is Microsoft's name for the same concept, introduced with COM and Windows. They are technically identical — a GUID is a UUID formatted the same way. The two terms are used interchangeably in practice. You'll see "GUID" in .NET, SQL Server, and Windows documentation, while "UUID" is more common in Linux, web, and open-source contexts.
Yes. UUID v4 and v7 generation uses crypto.getRandomValues(), the browser's CSPRNG (Cryptographically Secure Pseudo-Random Number Generator). This is the same entropy source your operating system uses for TLS key generation. It is fundamentally different from Math.random(), which is a predictable PRNG and must never be used for security-sensitive identifiers.
Yes, completely free. There are no usage limits, no account required, and no paid tiers. You can generate up to 100 UUIDs at a time and download them as a text file. The tool is ad-supported on the Oneyfy site, but all UUID generation functionality is fully available at no cost, with no restrictions on how many times you use it.
No data is ever sent to a server. All UUID generation runs entirely in your browser using the Web Crypto API. No network request is made when you click Generate. The UUIDs exist only in your browser's memory and are never transmitted or logged anywhere. You can verify this by opening your browser's Network DevTools tab and confirming no requests are made on generation.
Yes. The tool is fully responsive and works on modern mobile browsers including Chrome for Android and Safari for iOS. The Web Crypto API is supported by all current mobile browsers, so generation is just as cryptographically secure on mobile as on desktop. Tapping the Copy button on a UUID works with the mobile clipboard system.
Use UUID v5 when you need a deterministic UUID — one that always maps to the same input string. For example, if you want a stable UUID for the email address "[email protected]", you can generate a v5 UUID using the URL or DNS namespace plus that string. You'll get the same UUID every time, so you can recreate it later without storing it. UUID v4 is random every time, which is what you want for new, unique records.
The standard UUID format includes four hyphens separating the five groups of hex characters (e.g. 550e8400-e29b-41d4-a716-446655440000). Some systems store UUIDs as 32-character compact strings without hyphens (e.g. 550e8400e29b41d4a716446655440000) to save storage space or avoid parsing. The "No hyphens" toggle strips the dashes so you can copy the compact form directly.