UUID Generator — Random UUID & GUID Generator
Generate random UUIDs (v1, v4) online. Create single or bulk UUIDs for databases, APIs, and software development.
💻 Developer Tools
✅ Free
By SwiftCalcTools Editorial Team · Formula verified
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How to Use UUID Generator
- 1Enter the required values in the input fields above.
- 2Click the Calculate button or results update instantly as you type.
- 3View your results in the output panel below the inputs.
- 4Adjust any values to recalculate instantly.
Frequently Asked Questions
UUID v4 is randomly generated. 122 of 128 bits are random; the remaining 6 bits indicate version (4) and variant. The probability of collision is astronomically low (generating 1 billion UUIDs per second for 85 years gives a 50% chance of collision). Use v4 when you need unique IDs without coordination.
UUID v1 is time-based: it encodes the timestamp (100ns intervals since Oct 1582) + MAC address + clock sequence. This makes v1 UUIDs sortable by creation time but reveals the machine's MAC address (privacy concern). UUID v4 is fully random — no timing or machine information. For most web applications, v4 is preferred.
ULID (Universally Unique Lexicographically Sortable Identifier) is a 26-character base32-encoded ID: 10 chars timestamp (millisecond precision) + 16 chars randomness. Unlike UUIDs, ULIDs are lexicographically sortable (newer = alphabetically later). Great for database primary keys where you want time-ordering without exposing sequential IDs.
UUID v4 is fine but has trade-offs: larger than integer (16 bytes vs 4-8), random insertion causes B-tree fragmentation (slower inserts/updates). Solutions: use UUID v7 (time-ordered), ULID, or CUID2 for sortable random IDs. Alternatively use integer PKs with UUID as a separate external-facing column. PostgreSQL has a native UUID type that stores efficiently.