Free UUID Generator Online

What the UUID Generator Does

A UUID (Universally Unique Identifier) is a 128-bit value that serves as a globally unique label without needing a central authority to hand them out. Developers, database administrators, QA engineers, and system architects all reach for UUIDs when they need identifiers that will never collide, whether generated on one machine or a thousand.

This tool generates version 4 UUIDs — the most widely used variant — powered by your browser’s built-in cryptographic random number generator. Every UUID is created instantly on your device. No data is ever sent to a server. Your identifiers stay private, and the tool works even if you disconnect from the internet entirely.

If you have heard the term GUID (Globally Unique Identifier), it is the same concept. UUID is the name defined by RFC 4122; GUID is Microsoft’s label for the identical format.

How It Works

The interface is divided into a controls panel at the top and a results panel below it. Here is the step-by-step workflow:

1. Choose a quantity. The Quantity row offers preset buttons — 1, 5, 10, 25, 50, and 100. Click any preset to set how many UUIDs to generate in a single batch. One UUID is selected by default, so the tool is ready the moment the page loads.

2. Pick a format. The Format row provides four display options, shown with short labels that hint at the output style:

   • abc-def — lowercase with hyphens, the standard format (550e8400-e29b-41d4-a716-446655440000)
   • ABC-DEF — uppercase with hyphens, common in Windows and .NET environments (550E8400-E29B-41D4-A716-446655440000)
   • abcdef — lowercase without hyphens, a compact 32-character string (550e8400e29b41d4a716446655440000)
   • ABCDEF — uppercase without hyphens (550E8400E29B41D4A716446655440000)

   Switching formats does not regenerate your UUIDs. The underlying 128-bit values stay the same; only the display changes.

3. Hit Generate. The blue Generate button creates your batch immediately. The results panel lists each UUID in a monospace code block with a Copy button beside it. Click Copy on any row to place that single UUID on your clipboard — a brief checkmark confirms the action.

4. Copy in bulk. When you generate more than one UUID, a Copy All button appears at the top of the results panel. It copies every UUID as a newline-separated list, ready to paste into a SQL INSERT statement, a JSON array, a CSV column, or any configuration file that expects one identifier per line.

5. Review the info bar. Below the results, a compact info bar reminds you of the UUID v4 structure: xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx, where the 4 marks the version and the y position is always 8, 9, a, or b per the RFC 4122 variant specification.

Why Use Our UUID Generator

Runs 100% in your browser. Generation uses crypto.randomUUID() from the Web Crypto API — a cryptographically secure source of randomness built into modern browsers. No UUIDs are transmitted, logged, or stored on any server. Close the tab and they are gone.

No signup, no limits, no ads gating features. Generate 100 UUIDs at a time, switch formats freely, and copy results without creating an account or watching a countdown timer.

Cryptographic quality. UUID v4 provides 122 bits of randomness (6 bits are reserved for version and variant flags). The probability of generating a duplicate is roughly 1 in 2^122 — effectively zero for any practical workload.

Works offline and over HTTP. The tool includes a fallback that uses crypto.getRandomValues() when crypto.randomUUID() is unavailable, so it functions on plain HTTP connections and older browsers without sacrificing randomness quality.

Four format options in one place. Many online generators output only the default hyphenated lowercase format. This tool lets you toggle between all four common representations without regenerating, saving you a trip to a separate formatting tool.

Use Cases

• Database primary keys. Use UUID v4 values as primary keys in PostgreSQL, MySQL, MongoDB, or any datastore where you want identifiers that can be generated independently across microservices without coordination or collision risk.

• API resource identifiers. Expose UUIDs in REST or GraphQL endpoints instead of sequential integers. This prevents users from guessing resource IDs and avoids leaking information about record counts.

• Test data and seed scripts. Generate a batch of 50 or 100 UUIDs and paste them directly into seed files, migration scripts, or fixture JSON. The Copy All button formats them one per line for easy insertion.

• Session and correlation tokens. Assign a UUID to each user session, distributed trace, or log correlation ID. The cryptographic randomness ensures tokens are unpredictable and unique across services.

• File and asset naming. When users upload files, renaming them with a UUID avoids conflicts without parsing timestamps or incrementing counters. The compact (no hyphens) format works well for filenames on systems that are sensitive to special characters.

• Configuration and environment variables. Need a unique secret key, nonce, or placeholder value for a config file? Generate one here and copy it directly. No need to open a terminal or write a script.

Tips and Best Practices

• Use the standard format for storage, compact for URLs. The hyphenated lowercase format (abc-def) is the most portable and widely recognized. Switch to the compact format (abcdef) when you need shorter strings, such as in URL slugs or filenames.

• Do not rely on UUIDs as security tokens. While UUID v4 values are generated with cryptographic randomness, they are not designed to be secret. If you need an unguessable token (like a password reset link), pair a UUID with a separate cryptographic secret or use a purpose-built token generator.

• Store UUIDs efficiently in your database. Most modern databases support a native UUID column type that stores the value as 16 bytes rather than 36 characters of text. PostgreSQL’s uuid type, MySQL’s BINARY(16), and MongoDB’s UUID() all save storage and improve index performance.

• Generate in bulk when seeding data. Rather than generating one UUID at a time and pasting repeatedly, set the quantity to 25, 50, or 100 and use Copy All. It is significantly faster for populating test datasets.

• Verify your format matches the target system. Some platforms expect uppercase GUIDs (Windows registry, certain .NET libraries), while others require lowercase without hyphens (some NoSQL databases, URL-safe contexts). Pick the right format before copying to avoid unnecessary find-and-replace steps later.