What Is UUID (Universal Unique Identifier)?

April 10, 2024

A UUID, or Universal Unique Identifier, is a 128-bit number used to individually identify data in computer systems. It's designed to be globally unique, minimizing the chance of accidental duplication across different databases and systems, even those operating independently. This concept is crucial for data integrity and consistency, especially in large-scale deployments or distributed computing environments.

What Is UUID?

UUID is a standardized 128-bit format for string IDs that ensures uniqueness across various systems and databases. This format is commonly used in software development to assign unique identifiers without requiring significant central coordination. Imagine a vast library with countless books. Each book assigned a unique UUID would be easily identifiable and retrievable, regardless of its location on a shelf or if transferred to another library.


While UUIDs and Object Identifiers (OIDs) provide unique identifiers, they differ in structure and use.

UUIDs are 128-bit identifiers generated using algorithms that ensure uniqueness without centralized management. Lacking a central authority, they are ideal for scenarios where coordination is complex, such as software development and distributed systems where a flat, non-hierarchical format is required.

OIDs are hierarchical, dot-separated identifiers managed by registration authorities, suitable for structured environments like network management and telecommunications, where centralized control over namespaces is feasible. OIDs follow a hierarchical, assigned system managed by organizations, resulting in a tree-like structure. For instance, an OID might represent a specific company within a larger industry category.

How Does UUID work?

Specific algorithms create UUIDs to ensure each ID is unique. These algorithms may incorporate factors like the current time, network address of the host (MAC address), and random numbers. This approach, especially in versions 1 and 4 of the UUID specification, helps guarantee that identifiers are unique across all users and systems. Version 1 UUIDs, for example, leverage a combination of the machine's MAC address and timestamp, offering a high degree of uniqueness but potentially revealing some information about the generating machine. Version 4 UUIDs, on the other hand, rely solely on random numbers, making them unpredictable and anonymous.

What Is UUID used for?

Software development and database architecture leverage UUIDs to efficiently assign unique identifiers to information without significant overhead or coordination. 

These identifiers find common use in various areas:

  • Identifying database entries. For example, customer records on an ecommerce platform. Each record can have a UUID, ensuring no duplicates exist.
  • System components. Software modules benefit from unique identifiers provided by UUIDs.
  • Transactions. Tracking financial transactions or data updates becomes easier with UUIDs.
  • Synchronization across distributed systems. When data is replicated across multiple servers, UUIDs ensure consistency by guaranteeing unique identification.

UUIDs ensure each element is distinct and can be unmistakably referenced across different programs or components. For example, a social media platform might use UUIDs to identify individual user profiles, posts, and comments.

UUID Variants

UUID variants reflect the system's adaptability, each tailored for specific environments and uses.

Here is an overview of UUID variants:

  1. DCE standard. The predominant variant, set by the Distributed Computing Environment (DCE), caters to a broad spectrum of applications by using different generation methods. It's designed for robustness across distributed systems.
  2. NCS compatibility. To ensure backward compatibility with the older Network Computing System (NCS), one variant retains the NCS UUID format. This is crucial for systems that still interact with NCS-based UUIDs, though their usage is limited in new systems.
  3. Microsoft GUIDs. Microsoft's GUIDs are a specific case of UUIDs tailored for the Windows ecosystem. While similar to DCE-standard UUIDs, GUIDs may vary slightly, especially in older Microsoft software, to fit specific needs within Windows applications.
  4. Future variants. The UUID specification reserves bits for future expansion, allowing new variants to emerge as technology evolves. This ensures that the UUID system remains flexible and ready to adopt new generation methods or adapt to new technologies.

UUID Versions

There are five main UUID versions, each using different methods to guarantee uniqueness:

  • Version 1. Uses the host computer's MAC address and the current timestamp. While highly unique, it might reveal information about the generating machine.
  • Version 2. Like version 1, it includes additional information for DCE security.
  • Versions 3 & 5. Generated by hashing a namespace identifier (think category label) and a name (specific item within that category). Version 3 uses MD5, while version 5 uses SHA-1 (hashing algorithms). Depending on the chosen hashing algorithm, these versions offer some customization but might not be cryptographically secure.
  • Version 4. Created using random or pseudo-random numbers. This is the most common version due to its inherent randomness and anonymity.

UUID Advantages and Disadvantages

When deciding to use UUIDs in your systems, consider both their benefits and potential drawbacks.


Here are the benefits of UUID:

  • Uniqueness and decentralization. The design of UUIDs allows generation without a central authority, significantly reducing the chance of duplication. This is crucial for distributed systems or scenarios where central coordination might be impractical or undesirable.
  • Versatility. UUIDs can be employed in various applications, enhancing their utility across different systems. Their standardized format ensures compatibility across various software environments.


These are the drawbacks of UUID:

  • Size and readability. The 128-bit size of UUIDs makes them larger and less user-friendly than simpler identifiers like numerical IDs. Additionally, their format (e.g., 123e4567-e89b-12d3-a456-426655440000) is not easily human-readable. While this might not be an issue for internal system operations, it can be cumbersome for user-facing applications.
  • Potential predictability. Certain versions of UUIDs can inadvertently reveal information about when and where they were generated, posing a security or privacy risk in some contexts. Version 1 UUIDs, for example, encode the MAC address, which can be used to identify the network a device is connected to. This might not be a major concern for internal systems, but it could be an issue for anonymizing data or protecting user privacy.

How to Generate a UUID?

Generating UUIDs is straightforward across various development environments using built-in libraries or external tools designed for this purpose. Python offers the uuid library, providing a simple method for creating UUIDs in different versions, each suited for specific applications.

To generate a UUID, you would typically import the library, select the desired UUID version function (e.g., uuid4 for a completely random UUID), and call it to receive a unique identifier. This process allows developers to easily integrate unique identifiers into their applications without needing in-depth knowledge of the underlying generation algorithms.

Nikola is a seasoned writer with a passion for all things high-tech. After earning a degree in journalism and political science, he worked in the telecommunication and online banking industries. Currently writing for phoenixNAP, he specializes in breaking down complex issues about the digital economy, E-commerce, and information technology.