UUID Generator

Generate random UUIDs (v4) for databases, APIs, and applications. Cryptographically secure using Web Crypto API.

Number of UUIDs

Format Options

Uppercase No dashes With braces {}

Click generate to create UUIDs

What is a UUID?

A UUID (Universally Unique Identifier), also called GUID (Globally Unique Identifier), is a 128-bit label used to uniquely identify information in computer systems. It is formatted as 32 hexadecimal digits displayed in five groups: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx (8-4-4-4-12).

UUIDs are designed to be unique without requiring a central authority to coordinate assignments. The v4 variant (used by this tool) is randomly generated using a cryptographically secure random number generator, making collisions astronomically unlikely — there are 2^122 possible v4 UUIDs (about 5.3 × 10^36).

All UUIDs are generated locally in your browser using crypto.randomUUID() — the Web Crypto API. Nothing is sent to any server.

How to Use This Tool

Set the number of UUIDs you want to generate (1–100).
Choose format options: uppercase, no dashes, or with curly braces.
Click Generate.
Click Copy to copy all UUIDs to your clipboard.

UUID Versions Explained

v1 — Generated from current timestamp + MAC address. Exposes hardware identity and creation time. Rarely used today.
v3 — Name-based using MD5 hash. Deterministic: same input always produces same UUID. Used for stable identifiers from known names.
v4 (this tool) — Randomly generated. Most widely used version. No information encoded in the UUID.
v5 — Like v3 but uses SHA-1 instead of MD5. Preferred over v3 for new implementations.
v7 — Time-ordered random UUID. Monotonically increasing, which makes it much more efficient as a database primary key than v4.

Common Use Cases

Database Primary Keys — Enables distributed systems to generate IDs without a central sequence
API Resource Identifiers — Expose UUIDs in URLs instead of sequential IDs to prevent enumeration attacks
Idempotency Keys — Attach a UUID to API requests to prevent duplicate processing on retry
Session and Correlation IDs — Track requests across microservices for distributed tracing
File and Object Names — Generate unique filenames for uploaded content to avoid collisions

Frequently Asked Questions

Theoretically yes, but the probability is so small it's practically impossible. A UUID v4 has 122 bits of randomness (2^122 possible values). If you generated 1 billion UUIDs per second for 100 years, the probability of a single collision would still be less than 1 in a trillion. For all practical purposes, UUID v4 collisions don't happen.

It depends on your use case. Auto-increment integers are smaller (4–8 bytes vs 16 bytes), create better index locality, and are simpler. UUIDs allow distributed ID generation without coordination, prevent ID enumeration in public APIs, and make data merging from multiple databases trivial. UUID v7 (time-ordered) reduces the index fragmentation problem of random v4 UUIDs, making it a good compromise.

ULID (Universally Unique Lexicographically Sortable Identifier) is an alternative to UUID that encodes a millisecond timestamp in the first 48 bits, making ULIDs sortable by creation time. ULIDs use a base32 encoding, making them 26 characters vs UUID's 36 characters. They are useful as database primary keys where you want both uniqueness and sortability without a central sequence.

Yes, when generated with a cryptographically secure random number generator (CSPRNG) like the Web Crypto API used by this tool. However, UUIDs are identifiers, not secrets — they're not designed to be unguessable tokens for authentication. For security tokens (like password reset links or API keys), use a purpose-built secure random token generator rather than a UUID.

Yes. UUIDs are case-insensitive. 550e8400-E29B-41d4-A716-446655440000 and 550e8400-e29b-41d4-a716-446655440000 represent the same identifier. The RFC 4122 standard recommends lowercase, but you should use whatever case your system requires. Some databases and ORMs normalize to one case automatically.

UUID Generator

What is a UUID?

How to Use This Tool

UUID Versions Explained

Common Use Cases

Frequently Asked Questions

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