UUID Generator
Generate up to 100 UUID v4 (random) or v1 (time-based) identifiers at once, entirely in your browser. Copy any single UUID or the whole batch with one click.
No UUIDs yet — press Generate new to create a batch.
How UUID generation works
A UUID is a 128-bit identifier written as 32 hexadecimal digits in five groups of 8-4-4-4-12, like 3b241101-e2bb-4255-8caf-4136c566a962. Version 4 UUIDs fill 122 of those bits from a cryptographically secure random source; the remaining 6 bits are fixed to mark version 4 and the RFC 4122 variant. Version 1 UUIDs instead combine a 60-bit timestamp (100-nanosecond ticks since 15 October 1582), a 14-bit clock sequence, and a 48-bit node identifier.
Example: reading a v4 UUID
Take 3b241101-e2bb-4255-8caf-4136c566a962. The third group, 4255, starts with 4, so this is a version 4 UUID. The first nibble of the fourth group, 8 in 8caf, is binary 1000, marking the RFC 4122 variant. The remaining 122 bits — the rest of 4255, the rest of 8caf, and the full node group 4136c566a962 — are purely random, giving 2^122 (about 5.3 × 10^36) possible v4 values.
Frequently asked questions
What is a UUID v4?
A version 4 UUID is a 128-bit identifier made of 122 random bits, with 6 fixed bits that mark the version (4) and the RFC 4122 variant. That gives 2^122 — about 5.3 × 10^36 — possible values, so a random UUID generator can hand out identifiers with virtually no risk of collision.
What is the difference between UUID v1 and v4?
A v1 UUID is time-based: it combines a 60-bit timestamp counted in 100-nanosecond ticks since 15 October 1582, a 14-bit clock sequence, and a 48-bit node identifier, so values roughly sort by creation time. A v4 UUID is fully random apart from its version and variant bits. Most systems use v4 because it leaks no timing or hardware information.
Can I generate multiple UUIDs at once?
Yes. This bulk UUID generator produces between 1 and 100 identifiers per batch. Set the amount, click Generate new, then copy a single UUID with its Copy button or take the whole list with Copy all — convenient for seeding databases, fixtures, and automated tests.
How likely is a duplicate random UUID?
Practically impossible. You would need to generate about 2.71 quintillion (2.71 × 10^18) v4 UUIDs before the probability of a single duplicate reaches 50%. Even at 1 billion UUIDs per second, that takes roughly 86 years, so random UUIDs are safe for primary keys, request IDs, and trace IDs.
Are UUIDs good database primary keys?
Yes. PostgreSQL stores them in a native uuid column with the full 128 bits, while MySQL typically uses CHAR(36) or BINARY(16). A UUID written with hyphens is 36 characters; without hyphens it is 32. Random v4 keys also let your application create IDs before writing to the database, which simplifies imports and offline clients.
Do UUIDs contain private information?
Version 4 UUIDs contain no personal data — they are pure random output. Version 1 UUIDs do embed a creation timestamp and a 48-bit node identifier, which historically derived from a MAC address. If leaking generation time or hardware details matters to you, generate v4 instead of v1.
Are uppercase and lowercase UUIDs the same?
Yes. RFC 4122 treats hex digits in UUIDs as case-insensitive, so 3B241101-E2BB-4255-8CAF-4136C566A962 and its lowercase form are the same value. The uppercase toggle here formats output for systems or style guides that prefer capital letters; parsers accept either.
Does this online UUID generator store my results?
No. Every identifier is created locally in your browser from a cryptographically secure random source, and nothing is transmitted or saved on a server. Once the page has loaded, the generator even works offline, which suits internal identifiers and security-sensitive projects.