UUID Generator
Generate random UUID v4 values for use in databases, APIs, or testing.
How to use this UUID generator
- Set the number of UUIDs
Enter 1–10 in the Number of UUIDs field to specify how many identifiers to generate.
- Generate
The calculator produces random UUID v4 values using the browser's cryptographic random source.
- Copy the result
Copy the generated UUID(s) for use in databases, API payloads, or test fixtures.
How this UUID generator works
This tool generates version 4 UUIDs using browser randomness. UUID v4 identifiers are 128-bit values with specific bits set to indicate the version (4) and the standard variant used by modern UUID specifications. When Web Crypto is available, the randomness is cryptographically strong; otherwise the tool falls back to a weaker convenience-only generator.
UUID v4 = xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx (where y ∈ {8,9,a,b}) Example output: 550e8400-e29b-41d4-a716-446655440000
Generating 1 UUID yields a single value like a1b2c3d4-e5f6-4a7b-8c9d-0e1f2a3b4c5d. The 4 in the third group indicates version 4.
Generating 3 UUIDs returns three distinct values, each with 122 random bits. Use them as primary keys for test records or API resources.
- ✓ Uses the browser's cryptographic random number API when available.
- ✓ Falls back to Math.random() in environments without Web Crypto, which is suitable for convenience but not high-security use.
- UUID v4 is not sequential and not suitable for use as a sortable primary key in databases that benefit from ordered inserts.
Understanding UUID versions and structure
A UUID (Universally Unique Identifier) is a 128-bit value represented as 32 hexadecimal digits in five groups (8-4-4-4-12). Version 4 UUIDs use random or pseudo-random data for 122 of those bits; the remaining bits encode the version (4) and variant. The probability of a collision is astronomically low — about 1 in 2^122 — so UUIDs are effectively unique without coordination. Other versions exist: v1 uses timestamp and MAC address, v3 and v5 are name-based hashes, and v7 is time-ordered. UUID v4 is the most common choice for distributed systems because it requires no central authority and no shared state to generate.
Developer use cases for UUIDs
Developers use UUIDs as primary keys in databases, correlation IDs in distributed tracing, and unique identifiers in API payloads. Unlike auto-increment integers, UUIDs can be generated client-side or by any service without contacting a central database, which simplifies horizontal scaling and offline-first architectures. They are ideal for merge scenarios where multiple systems create records that are later combined. UUIDs also appear in OAuth state parameters, webhook signatures, and file naming to avoid collisions. When testing, generating UUIDs on demand avoids hardcoding and makes fixtures reproducible. The main trade-off is size (36 characters) and lack of sortability compared to sequential IDs.
Frequently asked questions
Are these UUIDs unique?
For all practical purposes, yes. The chance of generating a duplicate is astronomically small (1 in 2^122).
Can I use these in production?
Yes when the environment provides Web Crypto randomness. If the page is running without that API and falls back to Math.random(), treat the output as convenient identifiers rather than security-grade randomness.