UUID Generator
Quick answer: This generator creates RFC 4122 UUIDs instantly in your browser — five random v4 values per click by default. A v4 UUID looks like xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx, where the 13th hex digit is always 4 and y is one of 8, 9, a, or b. Choose v1 for time-based IDs, set the count (1–50) and format, and copy what you need.
Need unique IDs for database keys, API tokens, or test fixtures? Generate random v4 or time-based v1 UUIDs in bulk — up to 50 at a time — in lowercase, uppercase, or hyphen-free format. Everything runs locally; nothing is uploaded or logged.
Generator options
Generated UUIDs
Sample output — every click generates new values. Generated locally with crypto.getRandomValues; nothing leaves your browser.
How to use this generator
Pick v4 (random) or v1 (time-based), choose how many IDs you need, and select the letter case and hyphen style. New values appear instantly — click Generate again for a fresh batch.
Worked example — five v4 UUIDs generated when this page was built (sample output; every click generates new values):
b4cdd3b8-37c3-40c3-9be6-08b36fd107a8 5a4f9fac-0426-4edf-99d4-79d370769447 4309ea9b-922a-4cc1-b497-46058f71491b 95ae0ca5-ad0f-4ccc-8bfd-30b1b05b8bc0 64c15a76-1dd3-469d-941f-94bd53989729
Anatomy of a v4 UUID: xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx — the 13th hex digit is always 4 (the version), and y is one of 8, 9, a, or b (the variant). Check any of the samples above: each has a 4 in that position.
How it works
v4: 16 bytes from crypto.getRandomValues; the version bits are forced so the 13th hex digit is 4, and the variant bits so the 17th hex digit is one of 8, 9, a, b — exactly per RFC 4122 §4.1.3 and §4.4. v1: the current time as 100-nanosecond intervals since 15 October 1582, a random 14-bit clock sequence with the variant bits set, and a random 48-bit node ID. Formatting (case, hyphens) is cosmetic and never changes the underlying 128 bits.
Reference data
| Version | How it is generated |
|---|---|
| v1 | Timestamp + clock sequence + node ID (time-based) |
| v3 | MD5 hash of a namespace ID + name |
| v4 | 122 random bits |
| v5 | SHA-1 hash of a namespace ID + name |
Source: RFC 4122 (IETF) — rfc-editor.org.
Method & sources
v4 uses the browser's cryptographic RNG with the RFC 4122 version/variant bits set; v1 derives its timestamp field from the current clock per §4.1.4 with a random node and clock sequence. This generator implements v1 and v4 only — v3/v5 need a namespace and name input, which this page does not collect.
Frequently asked questions
What is a UUID?
A UUID (universally unique identifier) is a 128-bit ID written as 32 hexadecimal digits in five groups, like 550e8400-e29b-41d4-a716-446655440000. They are designed to be unique without any central registry handing them out.
What is the difference between UUID v1 and v4?
v1 embeds the current timestamp plus a random node ID, so IDs sort roughly by creation time but can reveal when and where they were made. v4 is 122 random bits — unpredictable, with no timestamp or machine info inside. Pick v4 unless you need time-ordering.
Can two UUIDs collide?
In practice, no. A v4 UUID has 122 random bits, so you would need to generate about 2.3 quintillion of them (2^61, the birthday bound) to reach even a 50% collision chance. For everyday use the risk is effectively zero.
Are these UUIDs safe to use as database keys?
Yes — random v4 UUIDs are a standard choice for primary keys and public IDs precisely because they are unique without coordination. Note that random UUIDs can fragment some database indexes; time-ordered IDs perform better there.
Is the randomness cryptographically secure?
The v4 values use crypto.getRandomValues, the browser's cryptographic random number generator. The v1 node ID and clock sequence are random per generation; the timestamp portion is not random by design.