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Authentication of CircleCI projects using the hosted application is handled by GitHub, Bitbucket, or Google OAuth. Sessions last for 14 days. See the Permissions Overview section of the GitHub and Bitbucket Integration document for additional details.

User authentication may use LDAP for an instance of the CircleCI application that is installed on your private server or cloud, see the Authentication document for setup instructions.

CircleCI Administrator

The first user to log into a private installation of CircleCI. Administrators have the ability to add and remove users.


A container is a running instance of an image.


Contexts provide a mechanism for securing and sharing environment variables across projects. The environment variables are defined as name/value pairs and are injected at runtime. Environment variables are set on the Contexts page. To use these variables in a workflow, users must be members of the context’s organization. The rule must allow access to all projects in the org. See the Contexts document for instructions.

Docker Layer Caching

The CircleCI Docker Layer Caching feature allows builds to reuse Docker image layers from previous builds. Image layers are stored in separate volumes in the cloud and are not shared between projects. Layers may only be used by builds from the same project. For additional information about how the secure environment is created, see the Docker Layer Caching and Running Docker Commands documents.

Environment Variables

Environment variables store customer data that is used by a project. Only project administrators and owners are allowed to view or modify environment variables. The values are transmitted using secure protocols, for example, HTTPS and SSH, encrypted at rest, and hashed/salted to prevent CircleCI employees from viewing them.


Defines the underlying technology to run a job. Can be either docker to run your job inside a Docker container with a specified image or machine to run your job inside a full virtual machine. Learn more.


An image is a packaged system that has the instructions for creating a running container.


A job is a collection of steps.

Job Space

All the containers being run by an executor for the current job.


CircleCI orbs are shareable packages of configuration elements, including jobs, commands, and executors. CircleCI provides certified orbs, along with 3rd-party orbs authored by CircleCI partners.


The owner of the team GitHub account or Bitbucket org.


CircleCI pipelines are the most high-level unit of work, encompassing a project’s full .circleci/config.yml file, including workflows, which coordinate jobs. Pipelines have a fixed, linear lifecycle, and are associated with a specific actor. Pipelines trigger when a change is pushed to a project that has a CircleCI configuration file included, and can also be scheduled, triggered manually through the CircleCI app, or using the API.

Pipelines are not available on installations of CircleCI server v2.x.

Primary Container

The first image listed in config.yml. This is where commands are executed for jobs using the Docker executor.


A CircleCI project shares the name of the code repository for which it automates workflows, tests, and deployment. It is visible on the Projects page of the CircleCI app and must be added with the Add Project button. After the project is added, it is possible to configure settings, contexts, environment variables, and team members who may follow the project. Following a project enables a user to subscribe to email notifications for the project build status and adds the project to their CircleCI dashboard.

Project Administrator

The user who adds a GitHub or Bitbucket repository to CircleCI as a Project.

Remote Docker

Feature that enables building, running and pushing images to Docker registries from within a Docker executor job. Learn more.


A step is a collection of executable commands. Learn more.


An individual user within an org. A CircleCI user is anyone who can log in to the CircleCI platform with a username and password. Users must be added to a GitHub or Bitbucket org to view or follow associated CircleCI projects.  Users may not view project data that is stored in environment variables.  


A Workflow is a set of rules for defining a collection of jobs and their run order. Workflows are implemented as a directed acyclic graph (DAG) of jobs for greatest flexibility. Learn more. Within the CI/CD industry, this feature is also referred to as Pipelines.


A workspace is a workflows-aware storage mechanism. A workspace stores data unique to the job, which may be needed in downstream jobs.

Help make this document better

This guide, as well as the rest of our docs, are open-source and available on GitHub. We welcome your contributions.