Question 1

What is a UUID and why should I use one?

Accepted Answer

A UUID (Universally Unique Identifier) is a 128-bit value used to uniquely identify information in computer systems. UUIDs are ideal for distributed systems because they can be generated independently without coordination, are practically guaranteed to be unique, and work across different databases and services. They are commonly used as database primary keys, session identifiers, and API request IDs.

Question 2

Which UUID version should I use?

Accepted Answer

For most applications, use UUID v4 (random) for general-purpose unique IDs. Use UUID v7 if you need sortable IDs for database primary keys (better indexing performance). Use UUID v5 when you need deterministic IDs that are always the same for a given input. Avoid UUID v1 if MAC address exposure is a security concern.

Question 3

What is the difference between UUID v4 and v7?

Accepted Answer

UUID v4 is entirely random using cryptographically secure random numbers, making it unpredictable but not sortable. UUID v7 includes a Unix timestamp in the first part, making it sortable by creation time, which improves database indexing performance. v7 is the newest specification and is recommended for modern applications that need time-ordered IDs.

Question 4

Are UUIDs really unique? Can collisions happen?

Accepted Answer

UUIDs are designed to be practically unique. For UUID v4, the probability of a collision is astronomically low - approximately 1 in 2^122 (5.3 x 10^36). You would need to generate billions of UUIDs per second for thousands of years to have a meaningful chance of collision. For practical purposes, UUIDs can be considered unique.

Question 5

Is this UUID generator secure and private?

Accepted Answer

Yes! All UUIDs are generated entirely in your browser using JavaScript. No data is transmitted to our servers or stored anywhere. The UUID v4 generator uses cryptographically secure random numbers from your browser's crypto API, making the generated UUIDs unpredictable and suitable for security-sensitive applications.

Question 6

How do I use UUID v5 with namespaces?

Accepted Answer

UUID v5 creates deterministic UUIDs by hashing a namespace UUID and a name using SHA-1. Select a standard namespace (DNS, URL, OID, or X.500) or provide a custom namespace UUID, then enter your name string. The same namespace + name combination always produces the same UUID, making it ideal for creating consistent IDs from names or URLs.

Question 7

What format should I use for storing UUIDs in databases?

Accepted Answer

For best performance, store UUIDs as binary (16 bytes) rather than strings (36-37 characters). Most databases have native UUID types (PostgreSQL, MySQL 8+) that handle this automatically. If your database doesn't support native UUIDs, use BINARY(16). This saves storage space and improves indexing performance compared to storing as VARCHAR.

UUID/GUID Generator

UUID Parser & Decoder

What are UUIDs?

UUID Structure

Common Use Cases

UUID Versions Explained

Timestamp + MAC Address

Random (Recommended)

Name-Based SHA-1

Unix Timestamp + Random (Modern)

UUID Best Practices

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Avoid These

Frequently Asked Questions

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Hash Generator

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Version	Method	Sortable	Deterministic	Privacy Safe
v1	Timestamp + MAC	Yes	No	No
v4	Random	No	No	Yes
v5	Name + SHA-1	No	Yes	Yes
v7	Timestamp + Random	Yes	No	Yes