Free UUID/GUID Generator
Last updated: March 16, 2026
A UUID generator creates random v4 universally unique identifiers for use in databases, APIs, and applications. Click generate to create one or more UUIDs instantly.
Generate random UUID v4 identifiers instantly. Bulk generate up to 100, uppercase or lowercase, with or without hyphens. Free online tool — no signup required.
Developers, designers, content creators, and anyone who needs to quickly generate text, codes, or identifiers.
100% free, runs entirely in your browser — no signup, no data sent to any server.
How to Use the UUID Generator Tool
UUID Generator Features and Options
About the Free Online UUID Generator
UUID v4 Anatomy
4 = version (always 4 for random UUIDs)
[89ab] = variant (RFC 4122)
x = random hexadecimal digit
122 random bits = 5.3 x 1036 possible UUIDs
How to Generate UUIDs Online
1. Set the quantity. Enter how many UUIDs you need, from 1 to 100. The default is 1 for quick single-use generation.
2. Click Generate. Your UUIDs appear instantly, each with its own Copy button for quick clipboard access.
3. Choose your format. Toggle between uppercase and lowercase, and between hyphenated and non-hyphenated formats. Changes apply to all generated UUIDs immediately.
4. Copy your UUIDs. Click Copy on any individual UUID, or use Copy All to get all UUIDs separated by newlines.
Understanding UUIDs in Software Development
UUIDs (Universally Unique Identifiers) solve a fundamental problem in software engineering: how to create unique identifiers without a central authority. In distributed systems where multiple servers, services, or devices need to create identifiers independently, sequential IDs like auto-incrementing integers break down. UUIDs allow any system to generate an identifier with virtual certainty that it will never collide with an identifier created anywhere else.
UUID versions serve different purposes. Version 1 uses the MAC address and timestamp, making it unique but revealing hardware information. Version 3 and 5 generate deterministic UUIDs from namespace and name inputs using MD5 and SHA-1 respectively. Version 4, which this tool generates, uses 122 random bits, making it the most widely used version for general-purpose unique identifiers. The newer Version 7 (RFC 9562) combines a Unix timestamp with random data, providing both uniqueness and chronological sorting.
Database primary keys are one of the most common uses for UUIDs. Unlike auto-incrementing integers, UUIDs can be generated on the client side before inserting into the database. This simplifies distributed architectures, allows offline ID generation, and prevents information leakage (sequential IDs reveal how many records exist). The trade-off is larger storage size (16 bytes vs 4-8 bytes for integers) and less efficient indexing due to randomness.
API design frequently uses UUIDs as resource identifiers in RESTful endpoints. Using UUIDs in URLs like /api/users/550e8400-e29b-41d4-a716-446655440000 is more secure than sequential IDs because they cannot be guessed or enumerated. This prevents IDOR (Insecure Direct Object Reference) vulnerabilities where attackers iterate through sequential IDs to access other users' data.
Beyond databases and APIs, UUIDs are used for browser session tokens, file upload naming, message queue correlation, distributed tracing, and idempotency keys that prevent duplicate API operations. Any situation where you need a unique identifier without consulting a central database is a good fit for UUIDs.
Frequently Asked Questions About UUID Generator
What is a UUID?
UUID stands for Universally Unique Identifier. It is a 128-bit value used to uniquely identify information in software systems. UUIDs are formatted as 32 hexadecimal digits displayed in five groups separated by hyphens, like 550e8400-e29b-41d4-a716-446655440000. They are designed to be unique across all systems without requiring a central registry.
What is the difference between UUID and GUID?
UUID (Universally Unique Identifier) and GUID (Globally Unique Identifier) are the same thing. UUID is the term used in the RFC 4122 standard and in most programming languages. GUID is the term Microsoft uses in Windows and .NET. They use the same format and generation algorithms.
What is UUID v4?
UUID version 4 generates identifiers using random or pseudo-random numbers. Of the 128 bits, 122 are randomly generated, 4 bits indicate the version (4), and 2 bits indicate the variant (RFC 4122). This creates 5.3 x 10^36 possible UUIDs, making collisions virtually impossible.
Can two UUIDs ever be the same?
While theoretically possible, the probability is astronomically low. With 122 random bits, you would need to generate about 2.71 x 10^18 (2.71 quintillion) UUIDs to have a 50% chance of a single collision. In practice, UUID v4 collisions are considered impossible for any realistic workload.
Should I use UUIDs with or without hyphens?
Both formats are valid. The hyphenated form (8-4-4-4-12) is the standard RFC 4122 format and is more readable. The non-hyphenated form saves 4 characters and is useful for compact storage, filenames, and URL parameters. Most databases and APIs accept both formats.
What are UUIDs used for?
UUIDs are used as database primary keys, API request identifiers, session tokens, file names for uploaded content, distributed system identifiers, message queue correlation IDs, and anywhere you need a unique identifier without checking a central database.
Are these UUIDs cryptographically secure?
Yes. This generator uses the Web Crypto API (crypto.randomUUID or crypto.getRandomValues), which provides cryptographically secure random numbers. The UUIDs generated are suitable for use as unique identifiers in any application.
Is my data sent to a server?
No. All UUID generation happens in your browser using the Web Crypto API. Nothing is sent to any server.
Related Free Online Tools
Generate UUIDs here, then use our other developer tools for hashing, encoding, and password generation.