UUID Generator
Generate one UUID or fifty in a single click, using your browser's cryptographically secure random number generator. Copy individual IDs or the whole batch, and switch to uppercase or hyphen-free formatting when your database or API demands it. Nothing is generated on a server.
Version 4 UUIDs generated with your browser's cryptographically secure random number generator. Nothing is sent to a server.
How to Use UUID Generator
Choose how many you need
Pick 1, 5, 10, 25, or 50 UUIDs from the count selector — a fresh batch generates immediately.
Adjust the format
Toggle Uppercase or No hyphens if your database or API expects a specific style. The whole list reformats instantly.
Copy what you need
Use the Copy button beside any single UUID, or Copy All to grab the entire batch as one ID per line.
About UUID Generator
What a version 4 UUID is
A UUID (universally unique identifier) is a 128-bit value written as 32 hexadecimal digits in a 8-4-4-4-12 pattern. Version 4 UUIDs are generated from random data: of the 128 bits, 122 are random while 6 are fixed to mark the version and variant. That gives about 5.3 undecillion possible values — enough that you can generate IDs on a thousand disconnected machines simultaneously with no realistic chance of collision. This is why v4 UUIDs are the default choice for database primary keys, distributed systems, and any place IDs must be minted without coordination.
Why the randomness source matters
Not all random is equal. This tool uses crypto.randomUUID(), the browser API backed by the operating system's cryptographically secure random number generator, with a crypto.getRandomValues() fallback for older browsers. That's important because UUIDs generated with weak randomness — like Math.random() — can be predicted or collide far more often than the math suggests. If your UUIDs ever appear in URLs, session identifiers, or anything an attacker might try to guess, cryptographic-quality randomness isn't optional.
Formatting for real-world systems
Different systems want UUIDs in different shapes. The canonical form is lowercase with hyphens, and RFC 4122 specifies lowercase output. But Microsoft SQL Server displays GUIDs in uppercase, some APIs compare IDs case-sensitively, and hex-string database columns often store the 32 characters without hyphens to save space. The uppercase and no-hyphens toggles reformat your generated batch instantly, so you can match your target system's convention without piping output through a text editor. All generation happens locally in your browser — the IDs exist nowhere else until you paste them.
Common uses for UUID Generator
- Generate primary keys for database records and migration seed data
- Create unique request and correlation IDs for logging and tracing
- Produce test fixture IDs for unit and integration tests
- Mint unique identifiers for files, sessions, and API resources
- Fill spreadsheets or mock data sets with batches of guaranteed-unique IDs
Frequently Asked Questions
Can two generated UUIDs ever collide?
Theoretically yes, practically no. With 122 random bits, you'd need to generate about 2.7 quintillion UUIDs to reach even a 50% chance of a single collision. Every UUID here comes from a cryptographically secure generator, so the math holds — there's no weak randomness quietly raising the real-world odds. Treat v4 UUIDs as unique without checking.
Are these UUIDs random enough for security purposes?
They're generated with crypto.randomUUID() or crypto.getRandomValues(), both backed by your operating system's secure random source — the same quality used for cryptographic keys. That makes them unpredictable enough for session identifiers or password-reset tokens. Still, purpose-built tokens with more entropy are the better practice for high-stakes secrets.
Should I use UUIDs as database primary keys?
They're excellent when you need IDs generated across multiple services without coordination, or want to avoid exposing sequential row counts. The trade-off: random UUIDs index less efficiently than sequential integers because inserts land at random positions in the B-tree. For write-heavy tables at scale, consider UUIDv7, which embeds a timestamp for sequential ordering.
What do the uppercase and no-hyphens options change?
Only the presentation — the underlying 128-bit value is identical. Uppercase suits systems like SQL Server that display GUIDs that way; removing hyphens produces the compact 32-character form used in hex database columns and some APIs. Most parsers accept any casing, but RFC 4122 specifies lowercase as the canonical output form.
Are the generated UUIDs stored or logged anywhere?
No. Generation happens entirely in your browser using local JavaScript — no server request is made, and no record of your UUIDs exists anywhere except your screen and clipboard. Refreshing the page produces a completely fresh, unrelated batch. This also means the generator keeps working offline once the page has loaded.