## Description Services are built once and then tagged, by default as `project_service`. If the Compose file specifies an [image](https://github.com/compose-spec/compose-spec/blob/master/spec.md#image) name, the image is tagged with that name, substituting any variables beforehand. See [variable interpolation](https://github.com/compose-spec/compose-spec/blob/master/spec.md#interpolation). If you change a service's `Dockerfile` or the contents of its build directory, run `docker compose build` to rebuild it.