Version 3: Name-based (MD5)


RFC 4122 states, “If backward compatibility is not an issue, SHA-1 is preferred.” As a result, the use of version 5 UUIDs is preferred over version 3 UUIDs, unless you have a specific use-case for version 3 UUIDs.


To learn about name-based UUIDs, read the section Version 5: Name-based (SHA-1). Version 3 UUIDs behave exactly the same as version 5 UUIDs. The only difference is the hashing algorithm used to generate the UUID.

Version 3 UUIDs use MD5 as the hashing algorithm for combining the namespace and the name.

Due to the use of a different hashing algorithm, version 3 UUIDs generated with any given namespace and name will differ from version 5 UUIDs generated using the same namespace and name.

As an example, let’s take a look at generating a version 3 UUID using the same namespace and name used in “Generate a version 5, name-based UUID for a URL.”

Generate a version 3, name-based UUID for a URL
use Ramsey\Uuid\Uuid;

$uuid = Uuid::uuid3(Uuid::NAMESPACE_URL, '');

Even though the namespace and name are the same, the version 3 UUID generated will always be 3f703955-aaba-3e70-a3cb-baff6aa3b28f.

Likewise, we can use the custom namespace we created in “Generate a custom namespace UUID” to generate a version 3 UUID, but the result will be different from the version 5 UUID with the same custom namespace and name.

Use a custom namespace to create version 3, name-based UUIDs
use Ramsey\Uuid\Uuid;

const WIDGET_NAMESPACE = '4bdbe8ec-5cb5-11ea-bc55-0242ac130003';

$uuid = Uuid::uuid3(WIDGET_NAMESPACE, 'widget/1234567890');

With this custom namespace, the version 3 UUID for the name “widget/1234567890” will always be 53564aa3-4154-3ca5-ac90-dba59dc7d3cb.


Version 3 UUIDs generated in ramsey/uuid are instances of UuidV3. Check out the Ramsey\Uuid\Rfc4122\UuidV3 API documentation to learn more about what you can do with a UuidV3 instance.