Online UUID Version 3 Generator

Generate Name-Based (MD5) UUIDs
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Understanding Your Online UUID Version 3 Generator

Welcome to our online UUID Version 3 generator! This tool empowers you to effortlessly create name-based (MD5) Universally Unique Identifiers (UUIDs) directly within your browser. UUID Version 3 identifiers are generated deterministically, meaning that if you use the same input 'namespace' and 'name', this UUID generator will always produce the exact same UUID. This predictability is a key feature of Version 3 UUIDs.

What is a UUID Version 3?

A UUID Version 3 is a specific type of universally unique identifier, as defined in RFC 4122. It is generated by hashing a 'name' and a 'namespace' identifier using the MD5 algorithm. Unlike randomly generated UUIDs (like Version 4), a UUID Version 3 is entirely deterministic. Given the identical namespace UUID and name string, any compliant generator will output the same 128-bit UUID. The core characteristic of this UUID version is its repeatability, making it highly suitable for scenarios where you need to consistently re-derive the same identifier from the same inputs without needing to store the generated UUID itself.

Why Use a Name-Based (MD5) UUID?

The primary advantage of employing a name-based UUID, specifically UUID Version 3 which utilizes the MD5 algorithm, lies in its deterministic nature. This offers several benefits:

  • Repeatability: You can reliably regenerate the exact same UUID if you possess the original namespace and name. This is invaluable for tasks such as data synchronization, content deduplication, or situations where an identifier must be consistently derived across different systems or at various times without explicitly storing the ID.
  • No Central Registry Needed: Unlike some identification systems, you don't require a central authority to issue or manage these UUIDs. As long as your chosen namespace is unique to your application's context, the UUIDs generated will be unique.
  • Content-Addressed Identification: In certain applications, the 'name' can represent the content or intrinsic properties of an object (e.g., a file's content hash, a unique business rule). The UUID Version 3 then serves as a stable identifier intrinsically linked to that specific content or name.

It's important to note that while MD5 is no longer considered secure for cryptographic purposes (like password hashing or digital signatures) due to known collision vulnerabilities, its use in UUID Version 3 generation is for creating unique identifiers, not for ensuring cryptographic security. For applications demanding a cryptographically stronger hash for name-based UUIDs, UUID Version 5 (which uses SHA-1) is the recommended alternative. However, for many common ID generation tasks where the primary concern is uniqueness and deterministic repeatability based on non-malicious inputs, UUID Version 3 remains a perfectly adequate and widely implemented standard. This online generator faithfully implements the RFC 4122 specification for UUIDv3.

How Our Online UUID Version 3 Generator Works

Using this online UUID Version 3 generator is a straightforward process:

  1. Provide a Namespace UUID: In the "Namespace UUID" field, enter a valid UUID that will act as the 'scope' or 'context' for your name. You can use one of the predefined RFC 4122 namespaces (e.g., for DNS, URL, OID, X.500 names, which are listed in Appendix C of the RFC) or a custom UUID that you've designated for your specific application. Our generator defaults to the DNS namespace UUID (6ba7b810-9dad-11d1-80b4-00c04fd430c8) for convenience.
  2. Enter a Name: In the "Name" field, input the string (the 'name') that you wish to convert into a UUID Version 3 within the chosen namespace. This could be a domain name (if using the DNS namespace), a URL, a file path, a product SKU, or any other string that is meaningful and unique within your namespace's context.
  3. View Generated UUID: As you type, our online generator automatically takes these two inputs. It concatenates the namespace UUID (as a byte string) and the name string (UTF-8 encoded), computes the 128-bit MD5 hash of this combined data, and then sets the appropriate version (3) and variant (RFC 4122) bits to produce the final UUID Version 3.

The resulting UUID is instantly displayed below the input fields, ready for you to copy and utilize in your applications.

Namespace UUID

A predefined or custom UUID that acts as a scope for the name when you generate a UUID. RFC RFC 4122 defines several standard namespace UUIDs (e.g., for DNS, URL, OID, X.500) that our UUID generator can use. You can find these pre-defined namespaces in Appendix C of the RFC.

Choosing an appropriate namespace is crucial for ensuring the global uniqueness of your generated UUIDs if the names themselves are not globally unique. For instance, if you are generating UUIDs for domain names, you should use the DNS namespace (6ba7b810-9dad-11d1-80b4-00c04fd430c8). If generating UUIDs for URLs, use the URL namespace (6ba7b811-9dad-11d1-80b4-00c04fd430c8). For custom applications, a common practice is to generate a random UUID (e.g., a Version 4 UUID) once and then use that fixed UUID as your unique namespace for all subsequent UUID Version 3s related to that specific application or dataset. This ensures that your name-based UUIDs won't collide with those generated in other contexts or by other applications that might happen to use the same names but under different, distinct namespaces. Our online tool allows you to input any valid UUID as a namespace.

Name

An input string that, when combined with the namespace, is used by the UUID generator to create a unique identifier. This name should be in a canonical format if multiple representations of the same underlying entity exist, to ensure consistent UUID generation. For example, if the name is case-insensitive, you should normalize it to a consistent case (e.g., all lowercase) before using it with the generator.

MD5 Hashing

To generate the UUID Version 3, the namespace UUID (converted to its byte representation) and the name (typically UTF-8 encoded) are concatenated in a specific order (namespace first, then name). The MD5 hash of this combined byte string is then computed by the UUID generator. The MD5 algorithm produces a 128-bit hash value. This entire 128-bit value forms the basis of the UUID, with specific bits subsequently modified, as described below, to ensure it conforms to the UUID standard format.

Format Adaptation

Specific bits within the 128-bit MD5 hash are then altered by the UUID generator to conform to the standard UUID Version 3 format as specified in RFC 4122. These modifications are crucial for interoperability:

  • Version Bits: The four most significant bits of the 7th byte (time_hi_and_version field) are set to 0011 (binary), which corresponds to hexadecimal '3'. This explicitly marks the UUID as Version 3.
  • Variant Bits: The two most significant bits of the 9th byte (clock_seq_hi_and_reserved field) are set to 10 (binary). This identifies the UUID as an RFC 4122 variant (specifically, the Leach-Salz variant).

These modifications ensure that any system or library designed to parse UUIDs can correctly interpret its version and structure, distinguishing it from other UUID versions or non-standard identifiers. Our online UUID Version 3 generator performs these adaptations automatically.

The format for a UUID Version 3 generated by our tool is xxxxxxxx-xxxx-3xxx-xxxx-xxxxxxxxxxxx. The '3' in the third group of hexadecimal digits clearly indicates that you've generated a Version 3 UUID.

Use Cases for UUID Version 3

Generating a UUID Version 3 is particularly useful when you need to create a consistent, unique identifier for a given name within a specific context (namespace). This makes this UUID version, produced by a UUID generator, valuable for scenarios requiring stable and repeatable IDs across different systems or over extended periods.

For example, if you are cataloging digital assets and need a persistent ID based on their original filename within a defined project namespace, UUIDv3 ensures that if the asset is processed multiple times, it always receives the same identifier from the generator. Other common uses include:

  • Generating stable identifiers for objects derived from X.500 distinguished names (using the X.500 namespace).
  • Creating unique IDs for URLs (using the URL namespace) for tracking or referencing purposes.
  • Identifying software components or interfaces based on their fully qualified names within a custom application namespace.
  • In distributed systems where different nodes need to independently generate the same ID for the same logical entity based on a shared naming convention and namespace.
  • Mapping external identifiers from other systems to a consistent UUID within your own system.

The key is that whenever you have a 'name' that is unique within a 'namespace', and you need an ID that can be regenerated without being stored, UUID Version 3, as created by this online generator, is an excellent choice.