UUID Generator — Tips & Guide

Generate cryptographically random UUID v4 identifiers for use in databases, APIs, distributed systems, and more. All generation happens in your browser.

Use UUIDs as Primary Keys

UUID primary keys prevent ID conflicts when merging databases or when multiple services create records simultaneously, making them ideal for distributed systems.

UUIDs in REST APIs

Use UUIDs in API endpoints instead of sequential integers to prevent enumeration attacks — an attacker can't guess /users/3 from /users/2 if IDs are UUIDs.

UUIDs for Session Tokens

UUID v4s make excellent short-lived session tokens and nonces because they are randomly generated and statistically unique without requiring a central counter.

File Naming with UUIDs

Use UUIDs as file names when storing user uploads to prevent collisions and avoid exposing original file names: e.g., 550e8400-e29b-41d4-a716.jpg.

Avoid UUIDs as URL Slugs

UUIDs are great for internal IDs but poor as human-readable URL slugs. Use them as hidden identifiers alongside a friendly slug for SEO-friendly URLs.

Copy Multiple at Once

Need a batch of UUIDs for seeding test data? Select 10 or 20 from the dropdown, generate, then copy all to get a ready-to-use list.

A UUID (Universally Unique Identifier), also called a GUID (Globally Unique Identifier), is a 128-bit number used to uniquely identify information in computer systems. It is typically written in the format xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx using 32 hexadecimal characters separated by hyphens. UUIDs are designed so that no two generated IDs will be the same, even across different machines and systems.

UUID v1 is generated from the current timestamp and the machine's MAC address — it is unique but can expose system information. UUID v3 and v5 are name-based, generated by hashing a namespace and name (MD5 or SHA-1). UUID v4 is randomly generated, with 122 bits of randomness, making it the best choice when you simply need a unique ID with no traceable origin. UUID v7 (newer) adds a sortable timestamp prefix, useful for database indexing.

UUID v4s are not absolutely guaranteed unique, but the probability of a collision is astronomically small. There are 2¹²² possible v4 UUIDs (about 5.3 × 10³⁶). To have a 50% chance of a single collision you would need to generate over 2.7 × 10¹⁸ UUIDs. For all practical purposes, UUIDs are unique.

Most databases support a native UUID type (PostgreSQL, MySQL 8+, SQL Server). Define your primary key column as UUID, then insert generated UUID values instead of auto-incrementing integers. In PostgreSQL use gen_random_uuid() or uuid_generate_v4(). In application code, generate a UUID before inserting a record and use it as the ID. This allows you to know the ID before the database insert completes.