Free Online UUID v4 Generator
Instantly generate one or up to 100 UUID v4 values. Choose between lowercase and uppercase output. All generation happens in your browser — nothing is sent to any server.
1 UUID generated
What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit label used to uniquely identify information in computer systems. It is standardized by RFC 4122 and appears in the format xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx, where each x is a hexadecimal digit.
UUIDs are designed to be unique across space and time without a central coordination authority, making them ideal for distributed systems, databases, and APIs.
UUID Versions
- v1 — Time-based. Generated from the current timestamp and the machine's MAC address. Can expose information about when and where it was generated.
- v4 — Random. Generated using a cryptographically secure random number generator. The most widely used version today — this is what this tool generates.
- v5 — Name-based (SHA-1). Deterministic — the same namespace + name always produces the same UUID.
How to Use
- Choose lowercase or UPPERCASE format.
- Set the count (1–100) for bulk generation.
- Click Generate to create new UUIDs.
- Hover over any row to copy a single UUID, or use Copy All to copy everything at once.
Frequently Asked Questions
How unique is a UUID v4?
A UUID v4 has 122 random bits, giving $2^{122}$ ≈ $5.3 \times 10^{36}$ possible values. The probability of generating a duplicate is astronomically small — roughly 1 in 5.3 undecillion.
Is a UUID the same as a GUID?
Yes. GUID (Globally Unique Identifier) is Microsoft's term for the same concept. They follow the same RFC 4122 format and are interchangeable.
Can I use UUIDs as database primary keys?
Yes. UUIDs are commonly used as primary keys in distributed databases because they can be generated on the client without needing a centralized sequence. However, random UUIDs (v4) can cause index fragmentation in some databases — consider UUID v7 or ULID for ordered alternatives.
Is my generated UUID truly unique?
UUID v4 uses crypto.randomUUID(), which is a cryptographically secure random number generator built into modern browsers. The statistical probability of collision is negligible for all practical purposes.