Build configurations define a build process for new Docker images. There are three types of builds possible - a Docker build using a Dockerfile, a Source-to-Image build that uses a specially prepared base image that accepts source code that it can make runnable, and a custom build that can run arbitrary Docker images as a base and accept the build parameters. Builds run on the cluster and on completion are pushed to the Docker registry specified in the "output" section. A build can be triggered via a webhook, when the base image changes, or when a user manually requests a new build be created.

Each build created by a build configuration is numbered and refers back to its parent configuration. Multiple builds can be triggered at once. Builds that do not have "output" set can be used to test code or run a verification build.