UUID v4 Generator
Generate a random UUID v4 instantly in your browser. Free, no signup.
How to use this tool
- Enter number of uuids in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your uuid(s) and the full breakdown beneath it.
UUID v4 (Universally Unique Identifier version 4) uses random bits to generate a unique identifier, giving you roughly 5.3 × 10^36 unique values.
How it works
UUID v4 Generator creates one or more universally unique identifiers using version 4, which generates each ID from cryptographically random bits. A UUID v4 looks like 550e8400-e29b-41d4-a716-446655440000 and has 122 random bits, making collisions astronomically unlikely even across billions of generated IDs.
Enter how many UUIDs you need and click Generate. The tool uses your browser's built-in crypto.getRandomValues API for high-quality randomness without any server call. Each result is a standard 8-4-4-4-12 hexadecimal format with the version and variant bits set correctly per RFC 4122.
UUIDs are used as primary keys in databases, identifiers for distributed system events, filenames for uploaded files, session tokens, and anywhere you need a unique ID without a central authority assigning it. Version 4 is the most widely used variant because it requires no input data and is simple to generate.
Worked example
Generate a batch of UUIDs for database seed data
- Enter 10 in the Number of UUIDs field.
- Click Generate.
- Copy the list of 10 UUIDs.
- Paste them into your database seed file or migration script as primary key values.
10 unique, RFC 4122-compliant UUID v4 strings ready for use as database identifiers.
Common mistakes to avoid
- Storing UUIDs as CHAR(36) in a database instead of a native UUID or BINARY(16) type: the text form uses 36 characters; native UUID columns are more efficient for indexing.
- Using a UUID as a session secret without additional entropy: while UUIDs are random, they are not specifically designed for security tokens; supplement with a longer random value for high-stakes secrets.
- Generating UUIDs by copying from this browser tool for production use instead of using a library: always generate UUIDs in your application code using a library (uuid in Node.js, uuid4 in Python) to avoid manual error.
Key terms
- UUID
- Universally Unique Identifier -- a 128-bit label standardized by RFC 4122, represented as 32 hexadecimal digits grouped with hyphens.
- Version 4 UUID
- A UUID generated from random or pseudo-random numbers. The version nibble is set to 4 and two variant bits are fixed; the remaining 122 bits are random.
- RFC 4122
- The Internet standard that defines the UUID format and its five versions, including version 4 (random) and version 1 (time-based).
Frequently asked questions
- What is UUID v4?
- UUID v4 is a randomly generated unique identifier in the format xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx, defined by RFC 4122.