UUID Generator

Generate random UUIDs (Universally Unique Identifiers) version 4 instantly. Bulk generation supported.

UUID v4 Generator

Generate distinct, cryptographically unique identifiers.

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How to use UUID Generator

1
Select the number of UUIDs you need.
2
Click "Generate UUIDs".
3
Click "Copy All" to save them to your clipboard.

Frequently Asked Questions

Are these UUIDs globally unique?

Yes — Version 4 UUIDs are generated using cryptographically secure randomness (crypto.randomUUID()). The probability of generating two identical UUIDs is astronomically low — about 1 in 5.3 undecillion.

What is the difference between UUID versions?

v1 is timestamp-based (deterministic but reveals time and MAC address). v3/v5 are name-based and deterministic. v4 is fully random — suitable for database primary keys, session tokens, and any use case where unpredictability is required.

Can I use these UUIDs as database primary keys?

Yes — UUID v4 is widely used as a primary key strategy in PostgreSQL, MySQL, MongoDB, and Firestore. Be aware that random UUIDs can cause B-tree index fragmentation at very high volumes; sequential UUIDs (ULIDs) avoid this.

Are UUIDs case sensitive?

No — UUIDs are case insensitive. Lowercase (standard) and uppercase representations are equivalent. Store consistently in one case (usually lowercase) to avoid inconsistencies.

Can I generate UUIDs in bulk?

Yes — select the count (up to any number) and click Generate. All UUIDs are generated locally in your browser and can be copied as a list.

Are the generated UUIDs sent to any server?

No — UUIDs are generated entirely in your browser using the Web Crypto API. Nothing is transmitted or logged.

Detailed Guide

Unique IDs When You Need Them, Without the Ceremony

Database migrations, test fixtures, API development, file storage systems — all of them need unique identifiers at some point. UUID v4 is the universally accepted standard for random, collision-proof IDs that don't require a central issuing authority or any database round-trip.

Set how many you need, click generate, copy them all. No signup, no API call, no network request.

What a UUID Looks Like

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A UUID is a 128-bit value expressed as 32 hexadecimal characters grouped by hyphens in the pattern 8-4-4-4-12. The total length is always 36 characters including hyphens.

In UUID v4, the third group always starts with 4 (indicating version 4), and the fourth group always starts with 8, 9, a, or b (indicating the RFC 4122 variant). All other hex characters are randomly generated.

The Randomness Behind UUID v4

UUID v4 uses the browser's CSPRNG (Cryptographically Secure Pseudo-Random Number Generator) via crypto.randomUUID() — the same source of randomness used for cryptographic key generation.

Collision probability: Two identical UUID v4 values would require generating approximately 2.71 quintillion UUIDs before reaching a 50% collision probability. For all practical engineering purposes, UUIDs are unique. No coordination with a central server is needed.

UUID Versions Compared

Version	Based On	Use Case
v1	Timestamp + MAC address	Time-ordered — but leaks hardware info
v3	MD5 hash of name + namespace	Name-based (deterministic)
v4	Random	Most common for application development
v5	SHA-1 hash of name + namespace	Name-based (more secure than v3)
v7	Timestamp + Random	Sortable UUIDs — new, gaining adoption

For general application use — primary keys, resource IDs, request traces — UUID v4 is the standard choice. If your database index performance is critical and you're inserting at very high volume, UUID v7's timestamp prefix solves the "random insert fragmentation" problem.

Real-World Use Cases

Database primary keys: UUID primary keys prevent ID enumeration attacks (attackers can't guess /users/1, /users/2...), make database sharding easier, and enable client-side ID generation before a row is inserted.

API request tracing: Assign a UUID as a X-Request-ID or Trace-ID header to every API call. This ties all log lines for a si...

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