About the UUID Generator
A UUID (Universally Unique Identifier) is a 128-bit value used to uniquely identify records across systems without central coordination. UUIDs power distributed databases, event streams, offline-first apps, and any system where sequential IDs would collide or leak information.
Versions v1 vs v4
UUID v1 combines the current timestamp with the host's MAC address and a monotonic counter. It is roughly sortable by creation time — useful for time-series indexing — but it leaks the generating machine and clock, which can be a privacy concern.
UUID v4 is generated from a cryptographically strong random source. It has no ordering, no host metadata, and a collision probability so vanishingly small that you would need to generate 2.71 quintillion IDs before a 50% chance of duplication. Use v4 by default.
When to use UUIDs
Use UUIDs when clients generate IDs (offline apps, mobile), when multiple databases merge, or when guessable sequential IDs would leak business signals (order counts, user growth). Their fixed size also makes them convenient for URL shorteners, session tokens, and idempotency keys.
Avoid UUIDs as clustered primary keys in write-heavy relational databases if you can help it — random insertion order fragments B-tree indexes. UUID v7, a newer time-ordered variant, mitigates this in modern engines.
Formatting output for different contexts
SQL and REST APIs typically expect the canonical hyphenated 8-4-4-4-12 form. C# GUIDs often use uppercase brackets like {AB12CD34-...}. C++/COM code may use quoted forms in header files. The formatting toggles let you produce all of these without post-processing.
Bulk generation is capped at 100 IDs per run to keep the browser responsive. For larger volumes, generate in the language of your target system rather than copy-pasting.
Step-by-step usage
1. Select v4 for random or v1 for time-based UUIDs. 2. Set the quantity between 1 and 100. 3. Toggle case, hyphens, quotes, and brackets to match your target format. 4. Click Generate. 5. Copy all with one click, or download as .txt or .json.
Frequently Asked Questions
For v4, you would need to generate about 2.71 quintillion (2.71 × 10^18) IDs to reach a 50% collision probability. In practice, collisions never happen.