Generate UUID v4 Online for Free
Need a unique identifier for a database record, API resource, or distributed system? Generate cryptographically random UUIDs in one click.
Quick Answer
Generate UUID v4, ULID, or NanoID values instantly at dotsapps.com. Each ID is cryptographically random with virtually zero chance of collision. Click to copy and use in your project.
What Is a UUID and When Do You Need One
A UUID (Universally Unique Identifier) is a 128-bit value formatted as 32 hex digits in 5 groups: 550e8400-e29b-41d4-a716-446655440000.
You need UUIDs when:
- Database primary keys — UUIDs let you create records without checking for conflicts, even across multiple servers.
- API resource IDs — Expose UUIDs in URLs instead of sequential numbers to prevent users from guessing other record IDs.
- Distributed systems — When multiple services create records independently, UUIDs ensure no collisions without coordination.
- Session tokens — Random UUIDs make unpredictable session identifiers.
UUID v4 (random) is the most common version. It uses random or pseudo-random numbers for all bits except the version indicator.
UUID vs ULID vs NanoID: Which to Choose
UUID v4 is the standard choice. 128 bits, universally recognized format, supported by every database and language. Completely random, so they don't sort in creation order.
ULID (Universally Unique Lexicographically Sortable Identifier) includes a timestamp component. They sort in creation order, which makes database indexing more efficient. Format: 01ARZ3NDEKTSV4RRFFQ69G5FAV (26 characters).
NanoID is a shorter alternative. The default is 21 characters using a URL-safe alphabet (A-Za-z0-9_-). Same collision probability as UUID but more compact. Great for URLs and user-facing IDs.
Use UUID when compatibility matters. Use ULID when you need sortable IDs. Use NanoID when you want shorter, URL-friendly IDs.
How Random Are UUIDs Really
UUID v4 has 122 random bits (6 bits are used for version and variant indicators). That means there are 2^122 possible UUIDs — roughly 5.3 × 10^36 possibilities.
To put that in perspective: if you generated 1 billion UUIDs per second, it would take about 100 years to have even a 50% chance of a single collision.
The tool at dotsapps.com uses crypto.getRandomValues(), which is a cryptographically secure random number generator built into your browser. This is the same randomness source used for HTTPS encryption.
For practical purposes, UUID v4 collisions simply don't happen in real-world applications.
Generating Multiple UUIDs at Once
Sometimes you need more than one UUID. Maybe you're seeding a database, setting up test fixtures, or creating a batch of resources.
The UUID generator at dotsapps.com lets you generate multiple IDs at once. Set the quantity you need and the format you want (UUID, ULID, or NanoID), and copy the entire batch with one click.
If you need UUIDs in code, here are the quick implementations:
JavaScript: crypto.randomUUID() — Built into modern browsers and Node.js 19+.
Python: import uuid; str(uuid.uuid4())
Command line: uuidgen on macOS/Linux.
How to Do It: Step-by-Step
- 1
Open the UUID Generator at dotsapps.com
- 2
Choose the ID format: UUID v4, ULID, or NanoID
- 3
Set the quantity of IDs you need
- 4
Click Generate to create fresh unique identifiers
- 5
Click Copy to grab the result for your project
Frequently Asked Questions
Can two UUIDs ever be the same?
Theoretically yes, but practically no. With 122 random bits, the chance of collision is astronomically small. You'd need to generate billions of UUIDs per second for decades to have a meaningful chance of one duplicate.
Should I use UUID or auto-increment for database primary keys?
Use auto-increment for simple single-server apps where performance matters most. Use UUIDs when you need IDs generated across multiple services, when you don't want sequential/guessable IDs, or in distributed systems.
What does UUID v4 mean?
The v4 indicates version 4, which means the UUID is generated from random numbers. Other versions use timestamps (v1), names (v3, v5), or a combination (v7). Version 4 is the most commonly used.
Are UUIDs URL-safe?
Standard UUIDs contain only hex characters and hyphens, which are URL-safe. However, they're long (36 characters). If you want shorter URL-friendly IDs, consider NanoID which is 21 characters by default.
What is the difference between UUID and GUID?
They're the same thing. GUID (Globally Unique Identifier) is Microsoft's term for UUID. The format, generation method, and properties are identical.
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