UUID Generator

GUID (Globally Unique Identifier) is Microsoft's name for the same concept. UUIDs and GUIDs follow the same RFC 4122 standard and are interchangeable in format (32 hex digits, 4 hyphens: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx). The term UUID is used in most programming contexts; GUID is common in Microsoft/.NET documentation and SQL Server. You may also see GUIDs formatted with surrounding braces: {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx} — the tool can output this format too.

Yes. The tool uses crypto.getRandomValues() from the Web Crypto API, which provides cryptographically secure pseudorandom numbers backed by the OS entropy source. This is the same randomness source used by ssh-keygen and password managers. Do not use Math.random() for UUID generation in production — it is not cryptographically secure and has been shown to produce predictable outputs in some JavaScript engines.

For UUID v4, collisions are theoretically possible but astronomically unlikely. The birthday problem tells us you would need to generate approximately 2.71 quintillion (2.71 × 10^18) v4 UUIDs to reach a 50% chance of a collision. At 1 billion UUIDs generated per second, that would take 85 years. In practice, UUID v4 is considered collision-free for all practical purposes. If you need guaranteed uniqueness without relying on probability, combine a UUID with a database-enforced unique constraint.

Auto-increment integers are simpler, smaller (4 or 8 bytes vs 16 bytes), and more efficient for clustered indexes because they insert in order. UUIDs have advantages: they work in distributed systems without coordination (two databases can generate IDs without talking to each other), they do not expose record count or creation order to clients, and they allow ID generation in the application layer before a database write. UUID v7 is the best of both worlds — random enough to avoid collisions, but sorted by timestamp so they cluster well in B-tree indexes. For most applications, the right choice is v7 for new distributed-system databases and auto-increment for simple single-server applications.

The variant field (bits 64-65 of the UUID) identifies which UUID specification was used to generate the identifier. Variant 1 (binary 10) is the RFC 4122 standard — all UUIDs you generate with this tool are Variant 1. Variant 0 was used in the obsolete NCS format. Variant 2 was used in Microsoft's GUID format (now equivalent to Variant 1). Variant 3 is reserved. When the validator shows "Variant: RFC 4122", the UUID is a standard compliant identifier. Variant information is mostly relevant when parsing foreign UUIDs from unknown systems.

Standard format with hyphens: 550e8400-e29b-41d4-a716-446655440000 (the default, most common). No hyphens: 550e8400e29b41d4a716446655440000 (used in some databases and APIs). Uppercase: 550E8400-E29B-41D4-A716-446655440000 (same value, different display). With braces: {550e8400-e29b-41d4-a716-446655440000} (Microsoft/COM style). All formats represent the same 128-bit value — only the string representation differs.

No. All UUID generation and validation runs in your browser using JavaScript and the Web Crypto API. No data, no generated UUIDs, and no validated UUIDs leave your device. The tool works fully offline once the page is loaded.