Anvil Tools
JSON Formatter & Validator
Pretty-print, minify, and validate JSON directly in your browser.
Open tool →UUID Generator
Create one or many RFC 4122 version 4 UUIDs using the browser’s cryptographically secure random-number generator.
Generate UUIDs
Recognize a version 4 identifier
550e8400-e29b-41d4-a716-446655440000 is a public format example, not a newly generated secret. A fresh batch should contain different values in the same shape. An application still needs uniqueness and authorization checks.
| Input or check | Expected result or decision |
|---|---|
| The first character of the third group is 4 | The version marker. |
| The first character of the fourth group is 8, 9, a, or b | The required variant bits in hexadecimal form. |
| Five hexadecimal groups: 8-4-4-4-12 | 36 characters including hyphens; an identifier does not grant access. |
| Case-insensitive format/version/variant check | ^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$; this does not authenticate the identifier. |
How it works
- Choose a count from 1 to 100.
- Each UUID uses secure random bytes and the required version and variant bits.
- Copy the list or download it as a plain-text file.
Common uses
- Creating database identifiers.
- Preparing unique IDs for test fixtures.
- Generating correlation IDs for development.
Your input stays in this browser. Nothing entered into this tool is sent to the Anvil Tools server.
A practical walkthrough
- Generate a batch of UUIDs for test records, then copy the values into your development dataset.
- Preserve the full identifier, including all hexadecimal groups, when moving it between systems.
- Copy the generated UUIDs or download the text file. Enforce uniqueness in your application when storing identifiers.
Tips for a reliable result
Random UUIDs have an extremely low collision probability, but a database should still enforce uniqueness. Identifiers are not passwords or access controls.
What to use next
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Open tool →How this tool handles your data
UUIDs are generated in your browser and are not sent to or stored by an Anvil processing server.
Known limitations
UUIDs are identifiers, not passwords, access tokens, or proof of uniqueness across every possible system. Randomness depends on supported browser cryptography.
Related guide and Lab test
Questions and troubleshooting
Are these UUIDs guaranteed never to collide?
No finite random identifier can offer an absolute guarantee, but version 4 UUIDs have 122 random bits, making accidental collisions extraordinarily unlikely when generated correctly.
Are they generated securely?
Yes. The tool uses crypto.randomUUID when available and a crypto.getRandomValues fallback with RFC 4122 version and variant bits.
When UUID generation is unavailable
Use a supported browser with cryptographic randomness and enter a count within the displayed range. Do not substitute a predictable counter when a random UUID is required. Save the generated list using Copy or Download; identifiers still need application access controls.
Can a UUID prove that someone owns a record?
No. An identifier names a record; authorization must still be checked by the application. Do not treat possession of a UUID as permission to access private data.
Do I still need a unique constraint?
Yes. Random version 4 UUID collisions are extremely unlikely, but storage should enforce uniqueness and handle conflicts rather than assuming they are impossible.
Explore practical guides and experiments
Are UUIDs Really Unique? Version 4 Collisions, Security, and Database IDs
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