How to Generate a UUID Online (Free)
UUIDs are 128-bit identifiers used to uniquely identify database records, API resources, and test fixtures without a central coordinator. This guide shows you how to generate one or a batch of UUIDs instantly — using cryptographically secure randomness built into your browser.
What Is a UUID?
A UUID (Universally Unique Identifier) looks like this:550e8400-e29b-41d4-a716-446655440000. It's 32 hexadecimal characters arranged in a 8-4-4-4-12 pattern. Version 4 UUIDs (the most common type) are randomly generated — there are 2¹²² possible values, making collisions astronomically unlikely.
They're used everywhere: as primary keys in databases, as resource IDs in REST APIs, as correlation IDs in distributed logs, and as idempotency keys in payment systems.
Step-by-Step Instructions
Open the UUID Generator
Navigate to the UUID Generator tool. It loads instantly and works offline once loaded.
Set the quantity
Use the quantity field to specify how many UUIDs you need. Enter 1 for a single UUID, or up to 100 for a bulk list — useful for seeding test databases or creating fixture data.
Click Generate
Click Generate. Each UUID is created using crypto.randomUUID() — the Web Crypto API built into every modern browser. This is the same entropy source used for generating cryptographic keys, so the randomness is genuinely strong.
Copy your UUIDs
Click Copy All to copy the entire list to your clipboard. Or click any individual UUID to copy just that one. You can also download the list as a plain text file.
Use in your project
Paste directly into your database seed file, JSON fixture, API test, or code. No formatting changes needed — the UUID is already in standard RFC 4122 format.
UUID Formats and When to Use Them
- Standard (hyphenated):
xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx— the default, accepted by virtually all systems. - No-hyphen (compact): 32 hex chars without dashes — used in some databases and URL paths where hyphens cause issues.
- Uppercase: Some legacy systems require uppercase hex. Both forms are equivalent.
- Nil UUID:
00000000-0000-0000-0000-000000000000— used as a placeholder or "no value" sentinel, not for real IDs.
Are These UUIDs Truly Unique?
UUID v4 uses 122 bits of randomness. The probability of two randomly generated UUIDs colliding is 1 in 2¹²² — far smaller than the chance of a hardware error corrupting your data. In practice, you'd need to generate billions of UUIDs per second for many years before a collision became statistically likely. For all practical application development, v4 UUIDs are unique.