UUID v1 vs. v4 and Bulk Generation
When to use UUID v1 versus v4, why collisions are effectively impossible, and generating bulk UUIDs for database seeding or testing.
NexifyTool Editorial Team
Web Utilities & Technical Publishing
UUID Generator creates RFC-standard universally unique identifiers using the widely-used uuid library, supporting both v1 (time-based) and v4 (random) formats, with bulk generation up to 10,000 at once.
v1 vs. v4 — which to use
UUID v4 is randomly generated and is the standard default for most use cases — database primary keys, API request IDs, session tokens — since it reveals nothing about when or where it was created. UUID v1 embeds a timestamp and is derived partly from the generating machine, which makes IDs naturally sortable by creation time but also means it leaks generation time as a side effect. Use v1 only if you specifically need that time-ordering property; use v4 for everything else.
Step-by-step
- Select v1 or v4.
- Set the quantity — from 1 to 10,000.
- Generate, then copy individual IDs or download the full batch as TXT or CSV.
Bulk generation for testing and seeding
Generating hundreds or thousands of UUIDs at once is useful for seeding test databases with realistic-looking primary keys, generating placeholder IDs for a mock API, or creating a batch of unique tracking codes.
Ready to generate one, or a batch? Open the free UUID Generator.
Frequently Asked Questions
What's the difference between UUID v1 and v4?
UUID v1 is time-based and includes a timestamp, making IDs naturally sortable by creation time but also revealing when they were generated. UUID v4 is fully random and reveals nothing about its origin.
Are UUID v4 values guaranteed to be unique?
Not mathematically guaranteed, but the probability of a collision is astronomically low — about 1 in 2^122 — making it a non-issue in practice.
How many UUIDs can I generate at once?
Up to 10,000 in a single batch, downloadable as TXT or CSV.
Which version should I use for a database primary key?
UUID v4 is the standard choice for most applications, since it doesn't leak generation time or machine information.