Generate cryptographically secure random UUIDs (version 4) directly in your browser. No server, no logs.
| # | UUID | Copy |
|---|---|---|
| Click "Generate Batch" to create multiple UUIDs | ||
crypto.randomUUID() (Web Crypto API). No data leaves your device. No cookies, no tracking.
A Universally Unique Identifier (UUID) version 4 is a 128-bit random number formatted as xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx, where the digit 4 indicates the version and y is one of 8, 9, A, B (variant 1). This standard (RFC 4122) ensures an astronomically low collision probability — approximately 5.3 × 10−36 for generating 1019 UUIDs. In practice, you could generate billions of UUIDs per second for millions of years before a collision becomes likely.
Total number of possible UUID v4: 2122 ≈ 5.3 × 1036
Probability of at least one collision after generating n UUIDs ≈ n2 / (2 × 2122). For n = 1019, probability ≈ 10−15.
While UUID v4 is the most widely adopted due to its excellent randomness and simplicity, different versions suit specific use cases. Choose based on your requirements (sorting needs, collision risk, performance).
| Version | Name | Randomness Source | Primary Use Case | Database Index Friendliness |
|---|---|---|---|---|
| v1 | Time-based + MAC | Timestamp + MAC address | Legacy system compatibility | Medium |
| v4 | Random (This Tool) | Cryptographically secure random | Universal identifiers, security tokens, distributed systems |
Low Randomness causes index fragmentation |
| v5 | Namespace-based (SHA-1) | Hash of namespace + name | Deterministic generation, content addressing | Medium |
| v7 | Timestamp-based + random | Unix timestamp + random | Time-ordered data, high-throughput databases |
Excellent Time-ordered reduces fragmentation |
crypto.randomUUID() (CSPRNG) – meets NIST SP 800-90A.
UUID v4 has been widely adopted as an industry standard. Here are some major implementation scenarios:
Systems like CockroachDB, Cassandra, and PostgreSQL (UUID type) use UUID v4 to avoid key collisions across shards. For a high‑volume e‑commerce platform generating 10 million orders/day, the chance of duplicate primary keys remains virtually zero over the platform's lifetime.
uuid_generate_v4() extension function, it's recommended to enable the uuid-ossp extension. For high-throughput write scenarios, consider time-ordered UUID v7 to reduce index fragmentation.
Microservices architectures rely on UUIDs to trace requests across services. A single correlation ID attached to each HTTP request helps debug latency and errors. Our batch generator can pre‑generate thousands of IDs for integration tests.
Because UUID v4 uses 122 random bits, they are resistant to brute‑force enumeration. Many OAuth2 implementations use UUIDs as state parameters to prevent CSRF attacks.
The generator uses the standard crypto.randomUUID() method available in all modern browsers (Chrome, Firefox, Safari, Edge). For older browsers (legacy fallback), a compliant implementation using crypto.getRandomValues() sets the version and variant bits as required by RFC 4122 Section 4.4:
0100 (hex digit 4 at position 14) as per RFC 4122 Section 4.1.3.
10xx → hex digit 8, 9, A, or B at position 19 as per RFC 4122 Section 4.1.1.
We have verified the output against known UUID v4 patterns and validated that the randomness source is non‑deterministic, seeded from system entropy (/dev/urandom on Unix, CryptGenRandom/BCryptGenRandom on Windows, SecRandomCopyBytes on iOS/macOS). The batch generator calls the same secure function repeatedly, ensuring each UUID is independent and unique with high probability.
Due to the complete randomness of UUID v4, using it as a primary key for high-volume sequential inserts can cause frequent index page splits (fragmentation), impacting write performance. For high-throughput time-series data, consider timestamp-prefixed UUID v7, which maintains global uniqueness while being time-ordered for better index performance.
Recommendation: For applications requiring high-throughput writes, consider using ordered UUIDs (like UUID v7) or composite keys (timestamp prefix + random suffix) at the database layer to reduce index fragmentation.
BINARY(16), SQL Server uniqueidentifier). However, random UUIDs may cause index fragmentation; consider using UUID v7 (time‑ordered) for write‑heavy workloads. For most applications, the benefits of global uniqueness outweigh the minor performance cost. Pro tip: In PostgreSQL, use the uuid data type and enable the uuid-ossp extension for uuid_generate_v4().
crypto.randomUUID() directly and compare with our output
All logic in this tool executes in your browser. You can view the complete source code via the browser's Sources panel and confirm via the Network panel that no network requests are made during generation, keeping your data completely local. This is the technical foundation of our user privacy commitment.
Independent Verification Guide: Advanced users can use the browser's Developer Tools (Console) to directly call crypto.randomUUID() for comparison, or use third-party RFC validation tools to verify generated results.
GetZenQuery follows a strict zero-data policy: all calculations happen in your browser, and we do not store or log any generated UUIDs. Our implementation is open for inspection (no obfuscation). The Web Crypto API is backed by the operating system's entropy sources, providing true randomness suitable for cryptographic applications.
Standardization History: The UUID standard was originally defined by the Open Software Foundation (OSF) in the DCE (Distributed Computing Environment) as GUID, later adopted by the Internet Engineering Task Force (IETF) as the RFC 4122 standard. Version 4 (random) became the most widely adopted due to its implementation simplicity and cryptographic security.