UUID v4 Generator
Generate cryptographically random UUID v4 identifiers instantly. Create up to 100 at once, copy individually or all at once — free, no sign-up, runs entirely in your browser.
Generate UUID v4
About UUID v4
UUID v4 (Universally Unique Identifier version 4) is a 128-bit random identifier formatted as xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx. The probability of collision is astronomically low — making them safe to use as primary keys, request IDs, or any unique identifier without coordination between systems.
Generated using the browser's crypto.randomUUID() API — cryptographically random, never leaves your device.
What is UUID v4?
A UUID v4 is a 128-bit randomly generated identifier formatted as xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx. The 4 marks it as version 4, and the randomness makes collisions statistically negligible.
Common use cases
UUIDs are used as primary keys in databases, correlation IDs in distributed systems, file upload names, and test data. They work across systems without a central coordinator.
When not to use UUIDs
UUIDs are not sequential, which can hurt database index performance on large tables. For high-throughput systems, consider ULIDs or sequential IDs instead.
How to use
- Set how many UUIDs you want to generate (1–100).
- Toggle "Uppercase" if needed.
- Click "Generate" to produce the UUIDs. Click "Copy All" to copy the full list to your clipboard.
Examples
- Simple: Generate 1 UUID →
550e8400-e29b-41d4-a716-446655440000. Notice the4in the third group, which identifies this as a v4 UUID. - Developer workflow: Need 10 seed records for a database fixture? Generate 10 UUIDs, click "Copy All", and paste them directly into your SQL insert script or JSON seed file.
- Edge case: Every v4 UUID has a
4as the first digit of the third group and an8,9,a, orbas the first digit of the fourth group. These are fixed version and variant bits — not random.
Frequently Asked Questions
- What is a UUID?
- A UUID (Universally Unique Identifier) is a 128-bit label used to uniquely identify objects in computer systems. Formatted as 32 hexadecimal digits in the pattern xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx, they are designed to be globally unique without a central authority.
- What is UUID v4?
- UUID v4 is the most common UUID version, generated from random or pseudo-random numbers. The "4" in position 13 identifies the version, and the variant bits in position 17 identify it as RFC 4122 compliant. The collision probability is so low it is effectively zero.
- Can I use UUIDs as database primary keys?
- Yes. UUIDs are commonly used as primary keys in distributed systems because they can be generated independently on any machine without risk of collision. The trade-off is slightly larger storage size (36 chars as text, 16 bytes as binary) compared to auto-increment integers.
- Are the generated UUIDs truly random?
- Yes. This tool uses the browser's built-in crypto.randomUUID() Web Crypto API, which generates cryptographically strong random UUIDs. No data is sent to any server.