UUID Generator (Version 4)
Generate one or many random RFC 4122 version 4 UUIDs and copy them individually or all at once. Everything runs locally in your browser.
Generated UUIDs
No UUIDs generated yet. Click Generate to create some.
How to Use the UUID Generator
A UUID (universally unique identifier) is a 128-bit value that labels data without relying on a central authority. This generator creates RFC 4122 version 4 identifiers directly in your browser and never sends anything to a server. Follow these steps.
Choose how many UUIDs you need. Enter a number between 1 and 100 in the count field; the default is 5. Example: enter 3 to produce three separate identifiers at once, which is handy when seeding a database table or preparing test fixtures.
Decide on letter case. Leave the uppercase box unchecked to get the standard lowercase form, or check it to receive values such as 550E8400-E29B-41D4-A716-446655440000. Example: log files and legacy systems sometimes expect uppercase, while most web APIs expect lowercase.
Click Generate UUIDs. The tool calls crypto.randomUUID() when your browser supports it and falls back to crypto.getRandomValues() otherwise. Both sources are cryptographically strong. Example: every click creates a fresh, unpredictable set, and no two runs will match.
Copy one value or all of them. Each row has its own Copy button, and Copy All places the entire list on your clipboard, one UUID per line, ready to paste into code, a spreadsheet, or a request body.
Pro tip: Version 4 UUIDs are built from random bits rather than a timestamp or machine address, so they never reveal when or where they were created.
What Is a UUID?
A UUID (universally unique identifier) is a 128-bit label rendered as 32 hexadecimal digits grouped into five sections, for example 123e4567-e89b-12d3-a456-426614174000. The format follows RFC 4122, which defines several versions. Version 4 is the most common: 122 of its 128 bits are random, while six bits are fixed to encode the version and the variant. That leaves roughly 2^122 possible values, so the chance of a collision is astronomically small — you could generate billions of UUIDs per second for years without a realistic risk of a duplicate. Because they need no central registry, UUIDs are ideal for distributed systems. A web server, a mobile app, and a background worker can each mint identifiers independently and safely merge their data later. They also make good opaque keys: unlike sequential integers, a UUID does not leak how many records exist or in what order they were created. It helps to distinguish a UUID from other random strings. A version 4 UUID has a fixed shape — hyphens in set positions, a "4" at the start of the third group, and a variant digit (8, 9, a, or b) at the start of the fourth group. A plain random hex string does not follow these rules and may be rejected by libraries that validate the canonical format.
Common Applications
1. Database primary keys: Applications use UUIDs as table keys so records can be created on the client or in any service without first asking a central database for the next number.
2. Distributed systems: Microservices, queues, and event buses tag messages with UUIDs so the same entity can be referenced unambiguously across independent components.
3. File and asset naming: Uploaded images, exports, and build artifacts are often stored under a UUID filename to avoid collisions and to prevent users from guessing other files.
4. Idempotency keys: Payment and messaging APIs accept a UUID as an idempotency key so a retried request is not processed twice, even if the network fails mid-call.
5. Testing and seeding: Developers generate batches of UUIDs to populate fixtures, mock API responses, and sample data with realistic-looking identifiers.
Version 4 vs Other UUID Versions
RFC 4122 defines several UUID versions. Version 1 combines a timestamp with a node identifier (often the MAC address), which can leak host information. Version 3 and version 5 are deterministic: they hash a namespace and a name with MD5 or SHA-1, so the same input always yields the same UUID. Version 4, produced here, is purely random and therefore the safest general-purpose choice when you do not need reproducible values.
Are UUID v4 Values Really Unique?
Version 4 UUIDs have about 3.4 x 10^38 possible values. To reach a one-in-a-billion chance of a collision you would need to generate around 2.6 x 10^15 UUIDs. In practice, applications that create only thousands or millions of identifiers will never see a duplicate. If your system needs guaranteed uniqueness, store the UUID as a primary key with a unique constraint and regenerate on the rare conflict.
Related Utilities
Frequently Asked Questions - FAQ
Are the generated UUIDs sent anywhere?
No. Generation happens entirely in your browser using built-in Web Crypto APIs. The values never leave your device and are never uploaded or logged.
What does "version 4" mean?
Version 4 is the random UUID variant defined by RFC 4122. It is built from 122 random bits plus six fixed bits that mark the version and variant, which is why v4 UUIDs cannot be predicted or reverse-engineered.
Can I generate more than one UUID at a time?
Yes. Enter any whole number between 1 and 100 in the count field, then click Generate. The tool creates that many independent UUIDs and lets you copy them all in one action.
Why would I use uppercase UUIDs?
Some legacy databases, log formats, and systems display identifiers in uppercase. Choose the uppercase option to match that convention; the underlying value is identical and case-insensitive when parsed.
Will two runs ever produce the same UUID?
For all practical purposes, no. The number of possible version 4 UUIDs is so large that a collision is far less likely than a hardware failure, so you can treat each generated value as unique.
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