How to generate UUIDs
- Type a number in the How many box, anything from 1 to 1,000, depending on whether you need a single ID or a whole batch of seed data.
- Tick UPPERCASE if your target system stores hex in caps, and Remove hyphens if it expects the compact 32-character form without dashes.
- Click ↻ Generate to fill the output box with a fresh set, one UUID per line, each drawn from your browser's cryptographic randomness.
- Press Copy all to grab the whole batch, then paste it into your code, a database seed, a spreadsheet column or a test fixture.
UUIDs exist to answer a specific problem: "I need a unique identifier right now, and I can't stop to ask a central database for the next number." Because a v4 UUID is generated purely from randomness, two different machines, or two different browser tabs, can each mint one at the same moment and be confident they won't clash, without any coordination between them. That property makes them the default choice for primary keys in distributed databases, identifiers in REST and GraphQL APIs, idempotency keys on payment requests, correlation IDs that stitch a single request across microservice logs, unique upload filenames, and stand-in data for tests.
Generating them here is instant and entirely local. The tool calls your browser's crypto.randomUUID, so every value is produced on your device with the same cryptographic-quality randomness used for encryption keys, nothing is fetched from or sent to a server. The Remove hyphens option matters more than it looks: some older systems, certain database column types and a few APIs store UUIDs as a bare 32-character hex string, and having the hyphen-free form ready saves a find-and-replace step later.
What a v4 UUID is, and why collisions basically never happen
A UUID is a 128-bit value written as 32 hexadecimal characters in the familiar 8-4-4-4-12 grouping, like 550e8400-e29b-41d4-a716-446655440000. In the version 4 variant, 6 of those bits are fixed to mark the version and variant, leaving 122 bits of pure randomness, about 5.3 undecillion (5.3×10³⁶) possible values. The odds of two collide are so small they're treated as zero in practice: to reach even a one-in-a-billion chance of a single duplicate, you would have to generate on the order of a billion UUIDs every second for around 85 years. That is why engineers assign v4 UUIDs freely without ever checking whether one already exists. The trade-off is that they are random, not sortable by creation time, if you need time-ordered keys, that's what newer schemes like UUIDv7 are for.
Frequently asked questions
What is a version 4 UUID?
It's a 128-bit identifier built almost entirely from random data, written as 32 hex characters in the 8-4-4-4-12 pattern, such as 550e8400-e29b-41d4-a716-446655440000. The "4" marks it as the random variant, as opposed to versions based on timestamps or a MAC address.
Are these UUIDs truly random and unique?
They come from your browser's cryptographic random number generator (crypto.randomUUID), the same grade of randomness used for security keys, not the predictable Math.random. Uniqueness is statistical rather than guaranteed, but with 122 random bits you'd need to generate billions every second for decades before a collision became likely.
Can I generate UUIDs in bulk?
Yes. Enter any count up to 1,000 and you get that many at once, one per line, ready to paste into a spreadsheet column, a SQL INSERT script or a batch of test fixtures. Everything is generated locally in your browser.
When should I use uppercase or remove the hyphens?
Use them to match whatever your target system expects. Some databases and legacy APIs store UUIDs as a bare 32-character hex string with no dashes, and a few compare hex case-sensitively. If you're unsure, the standard lowercase, hyphenated form is the safest default.
Should I use a UUID as a database primary key?
They're excellent when IDs must be created without a central counter, distributed systems, offline-first apps, or merging data from multiple sources. The main caveat is that random v4 values aren't chronologically ordered, which can fragment index locality on very large tables; if insert order matters, consider a time-sortable scheme.
Are UUIDs a secret or a security token?
No, treat them as identifiers, not passwords. A UUID may appear in URLs, logs and API responses, so never rely on one being unguessable to protect a resource. When you actually need a secret, generate one with the Password Generator instead.