UUID Generator
Generate secure random UUID v4 identifiers instantly. Runs locally in your browser.
Click Generate UUID to create one.What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit value formatted as 32 hexadecimal digits grouped by hyphens, like 3f2504e0-4f89-11d3-9a0c-0305e82c3301. It's a standard way to label something - a database row, a file, a request - with an identifier that's astronomically unlikely to collide with any other identifier, generated by anyone, anywhere, without needing a central authority to hand them out.
What is UUID v4?
UUID v4 is the random version of the UUID specification. Of the 128 bits, 6 are fixed to mark the version and variant, leaving 122 bits filled with cryptographically secure random data. There's no timestamp, no machine or network identifier, and no sequential pattern buried inside it - just randomness, which is exactly what makes it safe to generate from anywhere without coordinating with any other system.
How to generate a UUID
- Choose how many UUIDs you need from the quantity selector.
- Click Generate UUID.
- Copy a single UUID, or download the full list as a text file if you generated several.
- Click Generate Another any time to get a fresh batch.
Common use cases
- Primary keys for database rows, especially across distributed or sharded databases.
- Request IDs and trace IDs for tracking a single operation through logs and microservices.
- Session tokens, idempotency keys, and one-off identifiers for API calls.
- File and object names in storage systems, where you need to avoid naming collisions between uploads.
- Test fixtures and seed data, where you need realistic-looking unique values without a running database.
Why use a UUID instead of a sequential ID?
A simple auto-incrementing integer (1, 2, 3...) works fine as long as one database is the single source of truth handing out numbers. That assumption breaks down quickly in modern systems: if two services, two database shards, or an offline client and a server all need to create new records independently, they can't safely hand out sequential numbers without constantly checking in with each other. UUIDs sidestep the problem entirely - any client, server, or service can generate one on its own, with no coordination and no risk of two systems assigning the same ID. The tradeoffs are that UUIDs take more storage (16 bytes vs. 4-8 for an integer) and don't sort in creation order, so they're not a universal replacement - but for anything distributed, they remove an entire category of bugs.
How real is the collision risk?
In practical terms, negligible. With 122 random bits, the number of possible UUID v4 values is so large that even generating billions of them doesn't meaningfully raise the odds of a repeat - you'd need to create around a billion UUIDs every second for roughly 85 years before there's a 50% chance any two ever match. For nearly every application, the realistic risks are a bad random number source or a bug in how IDs are stored and compared, not the UUID scheme itself running out of room. That's also why this generator uses the browser's cryptographically secure random number API rather than a faster but weaker source.
Frequently asked questions
- Are UUIDs guaranteed to be unique?
- No scheme can guarantee absolute uniqueness, but UUID v4 gets close enough for practically any real workload. With 122 random bits, you'd need to generate roughly a billion UUIDs per second for about 85 years before the odds of a single collision reach 50%. For comparison, that's a far lower risk than a hardware failure corrupting your data.
- Is a UUID a secret?
- No. A UUID is random, but randomness alone doesn't make it safe as a password, API key, or access token. Treat UUIDs as identifiers that are safe to expose in URLs or logs, not as secrets that need to stay hidden.
- How is the randomness generated?
- This generator uses the Web Crypto API - crypto.randomUUID() where available, falling back to crypto.getRandomValues() - which pulls from your operating system's cryptographically secure random number generator. It never uses Math.random(), which is fast but not safe for anything where unpredictability matters.
- Why does this tool only generate UUID v4?
- Version 4 is the random variant, and it's what almost everyone means by "UUID" in everyday use - no timestamp, no machine identifier, no coordination required. Other versions exist (v1 is time-based, v5 is name-based via hashing) for more specialized needs, but v4 is the right default for primary keys, request IDs, and general-purpose unique identifiers.