UUID / GUID Generator
Generate version 4 or version 7 UUIDs in bulk, with custom formatting.
Generated entirely in your browser using the Web Crypto API’s secure random number generator — nothing is sent to a server or logged.
What a UUID (or GUID) Actually Is
A UUID (Universally Unique Identifier) — called a GUID (Globally Unique Identifier) in Microsoft’s ecosystem, but referring to the same standard — is a 128-bit number typically written as 32 hexadecimal characters split into five groups, like f47ac10b-58cc-4372-a567-0e02b2c3d479. Its entire purpose is to identify something (a database row, an API request, a file, a session) with a value that’s essentially guaranteed not to collide with any other UUID generated anywhere else, without needing a central authority to coordinate and hand out sequential numbers.
The Different UUID Versions, and Why v4 Is the Default
The UUID standard defines several versions built from different inputs, and they matter for different reasons:
| Version | Built from | Typical use |
|---|---|---|
| v1 | Timestamp + network card identifier | Legacy systems; largely avoided today since it can leak machine identity |
| v3 / v5 | A hash of a namespace + name | Generating the same UUID deterministically from the same input every time |
| v4 | Pure randomness | The default choice for most applications — database keys, API IDs, session tokens |
| v7 | Timestamp + randomness | Newer standard (finalized 2024); sortable by creation time, better for database index performance |
Version 4 is random enough that collisions are treated as effectively impossible for practical purposes — the random portion has 122 bits of entropy, meaning the number of UUIDs you’d need to generate before a collision became likely is so large it isn’t a real-world concern for typical applications.
Why UUID v7 Is Gaining Ground
A pure random v4 UUID has one practical downside as a database primary key: because each new value is scattered randomly across the entire 128-bit range, inserting new rows causes the database’s index to jump around unpredictably, which hurts performance at scale. UUID v7 solves this by encoding the current timestamp in the first part of the value, so UUIDs generated later always sort after ones generated earlier — giving you the collision-resistance of a UUID with the insert-friendly ordering of an auto-incrementing number. This is why newer systems are increasingly choosing v7 specifically for primary keys.
How This Tool Generates Them
Version 4 UUIDs use your browser’s native crypto.randomUUID() function where available, falling back to manually building one from the Web Crypto API’s secure random values on older browsers. Version 7 UUIDs are built by hand from your device’s current timestamp plus secure random bytes, following the version and variant bit layout defined in the UUID specification. Both approaches use a cryptographically secure random source — not a simple pseudo-random function — and nothing is generated on or sent to a server.
UUID / GUID Generator — FAQ
What’s the difference between a UUID and a GUID?
Nothing functionally — GUID is simply Microsoft’s name for the same 128-bit identifier standard defined by the UUID specification. The two terms are used interchangeably in practice.
Which UUID version should I use for a new project?
Version 4 (random) is the safe, well-supported default for most uses — API IDs, tokens, general-purpose unique identifiers. Consider version 7 specifically if you’re using the UUID as a database primary key and want better index performance from its time-sortable ordering.
How likely is a UUID collision?
For version 4 UUIDs, the random portion has 122 bits of entropy, making accidental collisions astronomically unlikely — low enough that virtually every system treats it as a non-issue in practice.
Why would I want a Nil UUID?
The Nil UUID (all zeros) is a defined constant in the UUID specification, commonly used as a placeholder value or to explicitly represent “no ID assigned” in a field that expects a UUID type.
Is it safe to generate UUIDs for production use with this tool?
Yes — it uses the Web Crypto API’s cryptographically secure random number generator (the same source used for security-sensitive operations in your browser), not a weaker pseudo-random function, and nothing generated here is transmitted or logged.