Frequently Asked Questions (FAQ)

What is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit number used to identify information in computer systems. The term GUID (Globally Unique Identifier) is also used and generally refers to UUIDs.

What are the different versions of UUIDs?

There are several versions of UUIDs, each generated using a different algorithm. The most common versions are:

• Version 1: Time-based and MAC address-based.
• Version 3 & 5: Name-based (uses a namespace and a name).
• Version 4: Randomly generated.
• Version 6: Reordered time-based for better indexing.
• Version 7: Unix epoch timestamp-based with random bits.
• Version 8: Custom format.

Which UUID version should I use?

The best version depends on your specific needs:

• Version 4 is often preferred when you need a statistically unique identifier without any external dependencies or the need to track generation order.
• Version 1 can be useful if you need some chronological ordering and can accept the potential privacy implications of including a MAC address.
• Version 3 & 5 are useful for generating the same UUID for the same input (namespace and name). Version 5 uses SHA-1 hashing, which is generally preferred over MD5 (used by Version 3).
• Version 6 & 7 are newer time-based versions designed to improve upon Version 1's indexing issues.

Are UUIDs truly unique?

While the total number of possible UUIDs (2¹²⁸) is extremely large, making collisions (generating the same UUID twice) highly improbable, they are not guaranteed to be absolutely unique. However, for practical purposes, the probability of collision is negligible.

How can I generate a UUID on UUID.ca?

Simply navigate to the page for the specific UUID version you need (e.g., UUID Version 4). Click the "Regenerate" button to create a new UUID. The generated UUID will be displayed in the input field, and you can copy it to your clipboard.

How can I decode a UUID?

Use our UUID Decoder tool. Paste the UUID you want to analyze into the input field and click "Decode." The tool will attempt to identify the UUID version and extract any relevant information (like timestamp for Version 1, 6, and 7).

Do UUIDs contain any personal information?

Typically, randomly generated UUIDs (like Version 4) do not contain any personal information. Version 1 UUIDs can potentially contain the MAC address of the generating device, which could be considered indirectly linked to a specific piece of hardware. Newer time-based versions like 6 and 7 aim to mitigate these privacy concerns.

Can I use UUIDs for database primary keys?

Yes, UUIDs are often used as primary keys in databases. They offer several advantages, such as avoiding conflicts when merging data from different sources and making it easier to distribute databases. However, depending on the database system and the UUID version used (especially older versions like Version 1), there can be performance considerations related to indexing.

Where are UUIDs commonly used?

UUIDs are used in a wide range of applications, including:

• Database identifiers
• Distributed systems
• Software development
• Tracking unique objects
• Content management systems
• API design