Generate UUID v1, v4, and ULID identifiers in bulk. Enter a number (1-50) for count.
Click generate and the tool produces a random version 4 UUID in the standard 8-4-4-4-12 hexadecimal format, like 3f2504e0-4f89-41d3-9a0c-0305e82c3301. UUIDv4 is derived from random bits, which makes each value practically unique across every system in the world without needing a database or coordinator. It's the go-to way to create primary keys, request IDs, and file names that will never clash even when generated independently.
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Quick answer
Click generate and the tool produces a random version 4 UUID in the standard 8-4-4-4-12 hexadecimal format, like 3f2504e0-4f89-41d3-9a0c-0305e82c3301. UUIDv4 is derived from random bits, which makes each value practically unique across every system in the world without needing a database or coordinator. It's the go-to way to create primary keys, request IDs, and file names that will never clash even when generated independently.
What is UUID / ULID Generator?
The UUID Generator is a free online tool that creates version 4 UUIDs — 128-bit identifiers built from cryptographically random values — that you can use as globally unique keys. Each UUID is virtually guaranteed to be unique without any central coordination, so multiple systems can generate IDs at the same time without collisions. Generation happens in your browser using a secure random source.
How to use UUID / ULID Generator
1
Generate a UUID
Click the generate button and a fresh version 4 UUID appears instantly. Each click produces a brand-new random value that is independent of every previous one.
2
Copy the value
Use the copy button to grab the full 36-character string, including the hyphens. The hyphens are part of the canonical format that most databases and libraries expect.
3
Use it as a key
Paste the UUID into your database insert, API request, config file, or file name. Because it's random, you don't need to check whether it already exists before using it.
4
Generate more as needed
Click again for each additional identifier you need. Every UUID is generated independently, so you can create as many as you want without any risk of them repeating.
Try it when you need to…
You need primary keys that clients can generate offline without round-tripping to the database for an auto-increment value
You want to trace one request across several microservices and need a unique correlation ID to attach to every log line
You need unique upload file names so simultaneous uploads from different users never collide
Use cases
Generate primary keys for database rows that can be created on the client or across shards without collisions
Create correlation or request IDs to trace a single request through distributed microservices
Produce unique file names or upload keys so concurrent uploads never overwrite each other
Seed test fixtures and mock data with realistic, non-repeating identifiers
Assign idempotency keys so a retried API call isn't processed twice
Key features
✓Generates RFC 4122 version 4 UUIDs from a cryptographically secure random source
✓Standard 36-character 8-4-4-4-12 hyphenated format ready to paste anywhere
✓One-click copy so you can drop the value straight into code or a database
✓Consistent lowercase hexadecimal output for predictable comparisons
✓Runs entirely in your browser with no account or API call required
Tips & best practices
A UUIDv4 carries no timestamp and no ordering. If you insert millions of them as a primary key, they scatter randomly across an index and can hurt insert performance — consider UUIDv7 or an ordered ID when index locality matters.
UUIDs are not secret or unguessable in a security sense beyond their randomness. Don't rely on a UUID alone as an access token; if a resource must be private, still enforce authorization checks.
The version 4 UUID has fixed bits: the 13th hex digit is always 4 and the 17th is one of 8, 9, a, or b. If those positions differ, the value isn't a standard v4 UUID.
Store UUIDs efficiently. In databases that support it, a native UUID or 16-byte binary column is far more compact than a 36-character string, saving space and speeding up comparisons.
Frequently asked questions
A UUIDv4 has 122 random bits, giving about 5.3 x 10^36 possible values. The probability of two randomly generated UUIDs colliding is so astronomically small that for practical purposes you can treat every generated value as globally unique, even across independent systems generating billions of them.
Version 1 is based on a timestamp and MAC address, version 4 is fully random, and the newer version 7 combines a timestamp prefix with randomness so the IDs sort chronologically. Version 4 is the most common general-purpose choice, while version 7 is preferred when you want database-friendly ordering.
Yes, and it's a common pattern that lets clients and distributed systems generate keys without central coordination. Be aware that random UUIDv4 values don't cluster in an index, which can slow inserts on very large tables — using a UUID column type or UUIDv7 helps mitigate that.
A UUIDv4 is generated from a secure random source, so it's hard to guess, but it isn't designed as a security credential and its format is well known. For sensitive access you should still enforce proper authorization rather than relying on the UUID being unguessable alone.
The version 4 identifier is encoded directly into the value: the first hex digit of the third group is always 4, marking it as a random UUID. The first digit of the fourth group is always 8, 9, a, or b, which encodes the variant. Those fixed positions let software recognize the UUID version at a glance.
No. The whole point of UUIDs is that their randomness makes collisions effectively impossible, so you can insert a freshly generated value without a uniqueness pre-check. This is what enables offline and distributed ID generation without a coordinator.
If your database has a native UUID type, use it — it stores the value in 16 bytes and compares faster than a 36-character string. When only text is available, a CHAR(36) or a stripped 32-character hex form works, but the native or binary form is more space- and index-efficient.