UUID Generator (v4)

Generate random, collision-free identifiers (UUID/GUID) — one at a time or in bulk, in the format you need.

Runs 100% in your browser — the generated identifiers are never sent anywhere.

What Is a UUID, and What Is It Used For?

A UUID (Universally Unique Identifier) is a 128-bit identifier standard that lets different systems — or the same system running at different times — generate identifiers independently, without needing a central registration authority. This tool generates the most widely used version, UUID v4: 122 bits of the identifier are fully random (coming from a cryptographically secure random number generator), while the remaining 6 bits carry version and variant information. The result is turned into the familiar format of 32 hexadecimal characters separated by hyphens into 8-4-4-4-12 digit groups (e.g. 550e8400-e29b-41d4-a716-446655440000).

UUIDs are most often chosen for distributed systems, where records are created independently — on different servers or by offline clients — and later merged, because unlike an auto-increment counter, two different machines will never produce the same identifier without needing any central coordination. Common uses include database primary keys (especially in microservice architectures where different services create records independently), "request ID"/"trace ID" values for tracking API requests end-to-end, session and token identifiers, and collision-free file names in file/object storage systems.

The chance of a collision is negligible in practice: 122 bits of randomness provides a huge probability space of 2¹²² — even if billions of UUIDs are generated at the same time, two of them colliding is mathematically almost impossible (by the birthday-paradox calculation, billions of UUIDs would need to be generated before a meaningful collision risk appears). That's why UUID v4 can be used safely without any extra uniqueness check.

This tool generates UUIDs using the browser's built-in Web Crypto API (crypto.randomUUID / crypto.getRandomValues, cryptographically secure randomness) — nothing generated is ever sent to a server or stored. You can generate up to 1000 UUIDs in bulk at once, export them with upper/lowercase and hyphenated/non-hyphenated/curly-braced (Windows GUID format) options, copy the result to the clipboard with one click, or download it as a .txt file.

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Frequently Asked Questions

UUID v4 is an identifier standard containing 122 bits of randomness. The number of possible combinations is so large (2122) that the chance of two separate generations producing the same UUID is negligible in practice — safe for uses like database primary keys, session IDs, or file names.

No, they're two names for the same standard. In the Microsoft ecosystem it's called "GUID" (Globally Unique Identifier), on other platforms "UUID" (Universally Unique Identifier); the format and generation logic are identical.

Auto-increment numbers are generated sequentially by a single database server; when multiple servers or microservices create records independently at the same time, there's a risk of collision. A UUID can be generated anywhere without any central coordination, which makes it the preferred choice for distributed systems, offline synchronization, and data merging; it also doesn't expose the total record count or let someone guess the next ID the way sequential numbers do when shown in a URL or API.

Yes — since UUIDs aren't sequential, they get inserted into a database index (B-tree) in random order, which can cause slightly more disk fragmentation and write-performance overhead than auto-increment on large tables; the 36-character text form also takes up far more storage than a 4-8 byte integer. For this reason, some systems use time-ordered alternatives like ULID instead of UUID to keep the benefit of sequential ordering.

UUID v1 is generated using the machine's MAC address and the current time (which can be a privacy concern, since it can reveal which device generated it and when); v3 and v5 are generated deterministically from a namespace and a string (using MD5 and SHA-1 respectively) — the same input always produces the same UUID. This tool generates v4, the most common and recommended version: fully random, untraceable, and non-deterministic.

No. Because UUID v4 is generated entirely at random, it's not deterministic — even with the same settings (count, format), clicking Generate again produces completely different identifiers. If you need to always derive the same ID from a specific piece of text (e.g. a file name), you need a deterministic v5 UUID, not a random v4.

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