Developer tool
UUID Generator
Generate UUID v4 identifiers with browser Web Crypto randomness. Choose a quantity, optionally uppercase letters or remove hyphens, then copy or download newline-separated UUIDs for fixtures, database rows, request IDs, test data, and development workflows.
Count
10
Length
36
Chars
369
Output
Generated IDs
UUID v4
Overview
What Is a UUID?
UUID stands for Universally Unique Identifier. A UUID is a standardized 128-bit identifier commonly displayed as hexadecimal characters separated by hyphens. Developers use UUIDs for API resources, database records, distributed systems, test fixtures, request IDs, and other cases where independently generated identifiers are useful.
This UUID Generator creates UUID v4 values with the browser's crypto.randomUUID() method. It can generate between 1 and 500 identifiers at a time, preserve canonical hyphenated lowercase output, or reformat the displayed strings as uppercase or hyphen-free values.
Format
UUID Format Explained
The common canonical UUID representation follows the pattern xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx. The M position indicates the UUID version. For UUID v4, that version digit is 4. The N position indicates the RFC-compatible variant family and is commonly one of 8, 9, a, or b in lowercase output.
This page can remove hyphens or uppercase the displayed text, but those options are presentation changes. The generated source UUIDs come from UUID v4 output produced by the browser API.
Versions
Supported UUID Versions
UUID v4
Supported. UUID v4 is the randomly or pseudorandomly generated UUID version defined by the UUID specification. This implementation uses crypto.randomUUID().
Other UUID versions
UUID v1, v3, v5, v6, v7, v8, nil UUIDs, namespace inputs, name inputs, and timestamp controls are not implemented on this page.
Method
How UUID Generation Works
- Enter a quantity from 1 to 500.
- Choose whether the displayed UUIDs should use uppercase letters.
- Choose whether to remove hyphens from the displayed UUID strings.
- Use Generate UUIDs to create a new newline-separated UUID v4 list.
- Copy the list or download it as uuids.txt.
Randomness
Randomness, Uniqueness, and Collisions
The page calls crypto.randomUUID(), which MDN documents as generating v4 UUIDs with a cryptographically secure random number generator. Random UUID uniqueness is still probabilistic: collisions are designed to be extremely unlikely when generation is correct, but not mathematically impossible.
A UUID is an identifier, not encryption and not a secret. Do not treat generated UUIDs as passwords, API keys, authentication tokens, or authorization proof simply because they are hard to guess.
Terminology
UUID vs GUID and Variant
UUID is the term used by the IETF specifications. GUID is historically associated with Microsoft ecosystems, and many practical tools use UUID and GUID to refer to the same general 128-bit identifier concept.
UUID version and UUID variant are different concepts. The version identifies the generation layout, such as v4 random UUIDs. The variant identifies the broader layout family used to interpret the UUID bits.
Examples
Common UUID Generator Examples
Database IDs
Generate identifiers for records when the application architecture benefits from non-sequential IDs.
API resources
Assign identifiers to resources returned or accepted by APIs.
Distributed systems
Create identifiers independently before data is merged across systems.
Development and testing
Generate UUIDs for fixtures, mock records, or sample payloads.
Correlation IDs
Use identifiers to connect related logs, events, or requests where appropriate.
Advantages
Benefits
- Generates UUID v4 identifiers without manual numbering.
- Supports bulk generation from 1 to 500 UUIDs.
- Provides uppercase and hyphen-free display options.
- Includes copy and download actions for quick reuse.
- Useful for development, testing, APIs, and distributed workflows.
Boundaries
Limitations
- Only UUID v4 generation is implemented.
- UUID validation and duplicate detection are not implemented.
- Random UUID uniqueness is probabilistic rather than absolutely guaranteed.
- UUIDs are larger and less human-readable than many integer IDs.
- UUIDs should not be used as secrets or credentials by default.
Guidance
Tips for Best Results
- Use UUID v4 when random identifiers fit the application requirements.
- Keep hyphenated canonical form when systems expect standard UUID strings.
- Validate UUIDs separately when accepting identifiers from external systems.
- Consider database indexing and storage implications for large UUID datasets.
- Do not use UUIDs as passwords, API keys, or bearer tokens.
Avoid
Common Mistakes
- Assuming UUIDs are guaranteed unique forever.
- Confusing UUID version with UUID variant.
- Assuming every UUID version is random.
- Using unsupported UUID versions on this page.
- Assuming uppercase and lowercase UUID strings identify different values.
Questions
FAQ
What is a UUID?
A UUID is a Universally Unique Identifier, a standardized 128-bit identifier commonly written as hexadecimal characters with hyphens.
What does UUID stand for?
UUID stands for Universally Unique Identifier.
What is a UUID Generator?
A UUID Generator creates identifiers using a specific UUID version and generation method. This page generates UUID v4 values.
What is UUID v4?
UUID v4 is the randomly or pseudorandomly generated UUID version defined by the UUID specification.
Does this tool support UUID v7?
No. This implementation supports UUID v4 generation only.
Is a UUID the same as a GUID?
In many software contexts, GUID and UUID refer to the same general 128-bit identifier concept, though terminology and platform behavior can differ.
Are UUIDs guaranteed to be unique?
No. Random UUID uniqueness is probabilistic. With appropriate generation, collisions are designed to be extremely unlikely, not impossible.
Can two UUIDs be the same?
Yes, a collision is possible in theory. Expected collision probability depends on the UUID version, randomness quality, and number generated.
Does the generator use cryptographically secure randomness?
Yes. The implementation calls crypto.randomUUID(), which MDN describes as generating v4 UUIDs with a cryptographically secure random number generator.
Can I use a UUID as a password or API key?
No. UUIDs are identifiers, not passwords, authentication tokens, API keys, or secrets by default.
Can I generate multiple UUIDs at once?
Yes. Enter a quantity from 1 to 500 and generate newline-separated UUIDs.
Can I validate a UUID?
No. This page generates UUIDs but does not include a UUID validation input.
Can I copy generated UUIDs?
Yes. Use the Copy button to copy the generated UUID list.
Can I download generated UUIDs?
Yes. Use Download to save the generated UUID list as uuids.txt.
Can I remove hyphens or use uppercase?
Yes. The page includes options for uppercase letters and removing hyphens from the displayed UUID strings.
Is the UUID Generator free?
Yes. This is a free browser-based UUID v4 generator.
Does the UUID Generator work on mobile devices?
Yes, when the browser supports the required Web Crypto API behavior used by crypto.randomUUID().
Are generated UUIDs stored on a server?
Generation runs in your browser and this tool does not intentionally upload or store generated UUIDs.
More Tools
Related Tools
Terms
Glossary
UUID
Universally Unique Identifier, a standardized 128-bit identifier.
GUID
A related identifier term commonly used in Microsoft ecosystems.
UUID Version
A field that identifies the UUID generation layout, such as v4.
UUID Variant
A field that identifies the UUID layout family.
UUID v4
The random or pseudorandom UUID version supported by this page.
Random UUID
A UUID generated from random or pseudorandom bits according to the version rules.
Cryptographically Secure Randomness
Randomness suitable for cryptographic use when provided by the platform API.
Collision
Two generated identifiers having the same value.
Identifier
A value used to refer to a resource, object, event, or record.
Hexadecimal
Base-16 notation using digits 0-9 and letters a-f.
Canonical UUID Representation
The common hyphenated textual UUID form.
UUID Validation
Checking whether a string matches expected UUID syntax and rules.
Sources
References
Transparency & Verification
Educational Disclaimer
This tool generates UUID v4 identifiers according to its implemented browser-based generation and formatting methods. UUID uniqueness is not an absolute mathematical guarantee, and UUIDs should not automatically be treated as passwords, authentication credentials, API keys, or secrets. Review generated identifiers against the requirements of the application using them.
Calculations and transformations execute locally on your machine with full offline support. Always verify critical results.
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