Self-hosted runners require both a namespace and a resource class.

A namespace is a unique identifier claimed by a CircleCI organization. Each CircleCI organization can claim one unique and immutable namespace. Typically, the namespace chosen is the lowercase representation of your organization’s name on your VCS (this is suggested).

A resource class is a label to match your CircleCI job with a type of runner that is identified to process that job. The first part of the resource class is your organization’s namespace. For example, a CircleCI resource class could be circleci/documentation. Resources classes are created when you go through the process of installing self-hosted runners.

Resource classes help you identify a pool of self-hosted runners, which allow you to set up your configuration to send jobs to specific places. For example, if you have multiple machines running macOS, and multiple machines running Linux, you could create resource classes for each of these, orgname/macOS and orgname/linux, respectively. At the job level in your .circleci/config.yml, you can associate which self-hosted runner resources to send a job to based on the resource class.

Optionally, you can give your resource class a description.