UUID Generator
Generate unique UUIDs instantly — one at a time or in bulk.
What is it?
A UUID (Universally Unique Identifier) is a 128-bit label used to uniquely identify information in computer systems. Also known as a GUID (Globally Unique Identifier) in Microsoft terminology, a UUID is designed to be unique across all space and time — meaning the same UUID should never be generated twice anywhere in the world, even without a central coordinating authority. UUIDs are used everywhere in software development: as primary keys in databases, as session tokens in web applications, as device identifiers in mobile apps, as transaction IDs in payment systems, and as correlation IDs in microservices logging. They follow a standardized format: eight hexadecimal characters, followed by three groups of four, followed by twelve — all separated by hyphens: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. This generator supports UUID version 4 (random) and UUID version 1 (time-based). Version 4 is the most widely used — it generates 122 bits of randomness, making collisions astronomically unlikely. Version 1 encodes the current timestamp and a node identifier, making it sortable by creation time. You can generate a single UUID or a batch of up to 100 at once, and choose between lowercase and uppercase output.
How to use it
- Choose your UUID version: v4 (random, most common) or v1 (time-based, sortable).
- Set the quantity — generate from 1 to 100 UUIDs at once.
- Choose the case format: lowercase (standard) or UPPERCASE.
- Toggle the "Hyphens" option to include or remove the dashes between groups.
- Click "Generate" to create your UUIDs instantly.
- Click "Copy all" to copy the entire list to your clipboard, or click any individual UUID to copy just that one.
Why use this tool
Every developer eventually needs to generate a UUID — for seeding a database, creating a test fixture, populating a config file, or quickly testing an API endpoint that requires a unique identifier. Opening a terminal, writing a script, or navigating to a bloated website just to get a UUID is a waste of time. This tool generates UUIDs instantly in your browser using the Web Crypto API, which provides cryptographically secure randomness. The UUIDs are generated locally — nothing is sent to any server, and no two users will ever get the same UUID even if they use the tool simultaneously. This is the mathematical guarantee behind UUID v4 design. The bulk generation feature is particularly useful for developers who need to seed a database table, create multiple test records, or generate a set of unique tokens for testing. Copy all 100 UUIDs with one click and paste them directly into your code or spreadsheet.
Frequently asked questions
What is the difference between UUID v1 and v4?
UUID v1 is time-based: it combines a timestamp with a node identifier (often derived from the MAC address) to create a sortable, unique identifier. UUID v4 is purely random: it uses 122 bits of cryptographic randomness with no temporal or machine information. For most web applications, v4 is preferred because it does not leak any information about when or where it was generated.
Can two UUIDs ever be the same?
Technically yes, but the probability is so vanishingly small it is considered negligible in practice. UUID v4 has 2^122 possible values — roughly 5.3 × 10^36. You would need to generate about 1 billion UUIDs per second for 85 years before there is even a 50% chance of a collision. In practice, UUID collisions simply do not happen.
What is the difference between UUID and GUID?
They are functionally the same thing. GUID (Globally Unique Identifier) is Microsoft's name for the same standard. Both follow the RFC 4122 specification and have the same format and properties.
Are the UUIDs generated here cryptographically secure?
Yes. This tool uses the Web Crypto API (crypto.randomUUID() or crypto.getRandomValues()) to generate cryptographically secure random UUIDs. These are not generated by Math.random(), which is not cryptographically secure and should never be used for tokens or identifiers.
Can I use these UUIDs as database primary keys?
Yes. UUID primary keys are a common and well-supported pattern in PostgreSQL, MySQL, SQLite, MongoDB and most other databases. The main trade-off compared to sequential integer keys is slightly larger storage and less efficient index clustering for large tables.