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DevUtil

UUID Generator - Generate Random UUIDs (v4) Online

About the UUID Generator

UUIDs show up everywhere in modern software. Database rows, API request IDs, distributed tracing spans, file names, and session tokens all rely on universally unique identifiers to avoid collisions without a central authority. This generator creates version 4 UUIDs using your browser's crypto.randomUUID() API, which provides cryptographically strong random values. No data leaves your browser.

Need a handful of IDs for a seed script or a hundred for a load test? Set the count, choose your formatting preferences, and hit Generate. Each UUID appears in a copyable row, and a Copy All button grabs the entire batch in one click.

How to Use the UUID Generator

Set the number of UUIDs you need (1 to 100) in the count field. Check the Uppercase box if you want A-F instead of a-f. Check No Dashes to remove the standard hyphen separators. Click Generate to create a fresh batch. Use the Copy button next to any single UUID, or Copy All to grab every UUID on the list separated by newlines.

Features

  • Batch generation. Generate up to 100 UUIDs at once for seeding databases, writing tests, or populating fixtures.
  • Format options. Toggle uppercase and dashless output to match your project's conventions.
  • One-click copy. Copy a single UUID or the entire batch to your clipboard instantly.
  • Crypto-quality randomness. Uses the Web Crypto API for cryptographically secure random number generation.
  • Client-side only. All generation happens in your browser. Nothing is sent to a server.

UUID Format Reference

A standard v4 UUID looks like xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx, where each x is a random hex digit and y is one of 8, 9, a, or b. The 4 in the third group identifies the version. This format produces 122 bits of randomness, resulting in over 5.3 × 1036 possible values.

Frequently Asked Questions

What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit identifier standardized by RFC 4122. It is formatted as 32 hexadecimal digits displayed in five groups separated by dashes: 8-4-4-4-12. UUIDs are designed to be globally unique without requiring a central authority, making them a popular choice for database primary keys, API identifiers, session tokens, and distributed system coordination.
What is UUID version 4?
Version 4 UUIDs are generated using random or pseudo-random numbers. Six bits are fixed to indicate the version (4) and the variant (RFC 4122), leaving 122 random bits. This produces approximately 5.3 x 10^36 possible values, making collisions astronomically unlikely. This generator uses the Web Crypto API's randomUUID() method, which provides cryptographically strong randomness.
Are generated UUIDs truly unique?
In practice, yes. With 122 random bits, the probability of generating two identical v4 UUIDs is vanishingly small. You would need to generate about 2.71 quintillion UUIDs to have a 50% chance of a single collision. For all real-world applications, v4 UUIDs can be treated as unique.
Should I use UUIDs with or without dashes?
Both formats represent the same 128-bit value. The dashed format (550e8400-e29b-41d4-a716-446655440000) is the standard representation defined in RFC 4122 and is more readable. The dashless format (550e8400e29b41d4a716446655440000) saves four bytes of storage and is sometimes preferred in URLs or compact storage. Most databases and libraries accept both.
When should I use UUIDs instead of auto-incrementing IDs?
UUIDs are a good fit when you need to generate IDs on the client before inserting into a database, when merging data from multiple sources that may have conflicting sequential IDs, when you want IDs that do not reveal the total count or ordering of records, or when working with distributed systems where coordinating a sequence counter would be impractical.