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UUID Generator

Generate cryptographically secure UUID v4 values. Bulk generate up to 50.

Click Generate to create UUID v4 values
Generated using crypto.randomUUID() — cryptographically secure random values. UUID v4 has 122 bits of randomness; collision probability is negligible.

What UUIDs are used for

UUIDs solve the problem of generating unique identifiers across distributed systems without a central coordinator. Unlike auto-incrementing database IDs, UUIDs can be generated on any client, offline, without risk of collision.

  • Database primary keys — especially in distributed or multi-tenant systems
  • API keys and tokens — as a base for unique references
  • File names — avoiding conflicts in multi-user uploads
  • Session IDs and correlation IDs — for request tracing
  • Frontend generated IDs — for optimistic UI updates before server confirmation

UUID versions

There are several UUID versions. v1 includes a timestamp and MAC address.v3 and v5 are namespace-based (deterministic from input).v4 is fully random — the most commonly used. v7 (newer) is time-ordered and random, useful for database index performance.

This generator produces v4 UUIDs using crypto.randomUUID()— the browser's native CSPRNG-based implementation.

Common use cases for UUID generation

Backend developers generate test UUIDs to seed databases during development without needing a running database to produce auto-increment IDs. QA engineers create UUIDs for test fixtures that need stable, unique identifiers across test runs. Architects designing multi-tenant SaaS systems use UUIDs instead of auto-increment IDs to prevent enumeration attacks — if IDs are sequential, a bad actor can iterate through all records; UUIDs make this infeasible. Data engineers use UUID v4 as partition keys in distributed databases (Cassandra, DynamoDB) to avoid hot partitions.

UUID v4 vs v7 — which should you use?

UUID v4 is fully random — excellent for uniqueness but poor for database index performance because random inserts cause B-tree page splits. UUID v7 (RFC 9562) prefixes the UUID with a millisecond timestamp, making it time-sortable and dramatically better for sequential database inserts. If you are building a new system in 2025 and your database supports UUID v7 natively (PostgreSQL 17+, MySQL 8.0.35+), prefer v7 for primary keys. For legacy systems, API tokens, and non-database use cases, v4 is still the standard.

Bulk UUID generation tips

Use the bulk mode to generate up to 50 UUIDs at once. The “Copy All” button copies them as a newline-separated list, ready to paste into a SQL INSERT script, a seed file, or a spreadsheet. Toggle the hyphen option off if your database stores UUIDs as 32-character strings (common with MySQL's CHAR(32) column type). Toggle uppercase if your system expects uppercase hex (some older Oracle and SQL Server schemas).

Frequently asked questions

What is a UUID?
UUID (Universally Unique Identifier) is a 128-bit label used to uniquely identify objects in computer systems. The standard format is 8-4-4-4-12 hexadecimal digits separated by hyphens, e.g. 550e8400-e29b-41d4-a716-446655440000.
What is UUID v4?
UUID v4 is randomly generated — 122 bits of randomness with a small portion reserved for version and variant bits. It requires no coordination between systems, making it ideal for distributed databases, frontend IDs, and API keys.
Are these UUIDs truly unique?
The probability of generating two identical v4 UUIDs is astronomically small — roughly 1 in 5.3 × 10^36. For practical purposes in any application, they are effectively guaranteed unique.
Is crypto.randomUUID() safe to use?
Yes. crypto.randomUUID() uses the browser's cryptographically secure pseudorandom number generator (CSPRNG), the same source used for cryptographic operations. It is significantly more random than Math.random().
When should I use UUID without hyphens?
Some databases and APIs prefer the compact 32-character hex string without hyphens (e.g., MySQL's UNHEX for binary storage, some REST APIs). Both formats represent the same value — the hyphens are just separators for readability.

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