ko
What it is
ko is a free, open-source tool for building container images for Go applications. It runs `go build` on the local machine, so Docker does not need to be installed. The project says it is suited to a single Go application with few operating-system base-image dependencies, such as an application without cgo or OS package requirements. Builds can target all platforms supported by the configured base image or selected platforms such as linux/amd64 and linux/arm64. For Kubernetes workflows, `ko resolve` builds images for `ko://` references in YAML and replaces them with image references; `ko apply` can apply the resolved configuration. ko reuses the normal Go build cache and avoids pushing image blobs already present in the remote registry. It generates and uploads SPDX-format SBOMs by default, with an option to disable generation. Registry credentials can come from Docker configuration, with built-in environment credential support for Google, Amazon, Azure and GitHub registries. A Terraform provider supports Infrastructure-as-Code workflows. ko supports Go applications only and defaults to CGO_ENABLED=0. Windows container image support is described as experimental and requires a Windows base image.
For and against
For
- Builds Go container images without Docker installed
- Supports multi-platform builds
- Generates SPDX-format SBOMs by default
- Reuses the standard Go build cache
- Free and open source
Against
- Supports Go applications only
- Defaults to CGO_ENABLED=0
- Windows container image support is experimental
- Requires OS packages to be available in the base image
The verdict
ko offers a focused way to build Go container images locally, with Kubernetes workflows and SBOM generation. Its Go-only scope and base-image dependency requirements make it a specific fit rather than a general image builder.
Who it suits
ko suits developers building Go applications with limited dependencies on the operating-system base image. Its Kubernetes and Terraform integrations also suit teams using those workflows.
Plans and prices
ko
Open source Go container image builder
Read 5 Oct 2026 · ko.build
On the record
- Best fit
- ko is ideal for a single Go application with few or no dependencies on the operating system base image, such as applications without cgo or OS package dependencies.ko.build · read 5 Oct 2026
- Build cache
- ko reuses the normal go build cache and avoids pushing image blobs already present in the remote registry.ko.build · read 5 Oct 2026
- Build method
- ko runs go build on the local machine and does not require Docker to be installed.ko.build · read 5 Oct 2026
- Community support
- The project offers a bi-weekly community meeting and discussion in the #ko-build channel on Kubernetes Slack.ko.build · read 5 Oct 2026
- Debugging
- The --debug build flag adds Delve and debug symbols to the image and runs the app in debug mode on port 40000; the feature is intended for development, not production.ko.build · read 5 Oct 2026
- How it builds
- ko runs go build on the local machine and does not require Docker to be installed.ko.build · read 5 Oct 2026
- Ideal use
- ko is ideal for Go applications without many dependencies on the operating system base image, such as applications that do not use cgo or require OS packages.ko.build · read 5 Oct 2026
- Install platforms
- The installation guide documents Windows, macOS, and Linux installation options, including GitHub releases, package managers, and source installation.ko.build · read 5 Oct 2026
- Integrations
- ko provides a Terraform provider for using image builds in Infrastructure-as-Code workflows.ko.build · read 5 Oct 2026
- Kubernetes
- ko resolve replaces ko:// Go import paths in Kubernetes YAML with built image references, and ko apply can apply the resolved configuration.ko.build · read 5 Oct 2026
- Kubernetes workflow
- ko resolve builds images for ko:// references in Kubernetes YAML and replaces them with the resulting image references.ko.build · read 5 Oct 2026
- Limit
- ko only supports Go applications and works best when applications do not depend on the underlying image; builds use CGO_ENABLED=0 by default.ko.build · read 5 Oct 2026
- Limitations
- ko supports Go applications only, defaults to CGO_ENABLED=0, and requires OS packages to be available in the configured base image.ko.build · read 5 Oct 2026
- Multi-platform builds
- ko can build for all platforms supported by the configured base image or for selected platforms such as linux/amd64 and linux/arm64.ko.build · read 5 Oct 2026
- Project and community
- ko is a Cloud Native Computing Foundation Sandbox project, and its community page lists bi-weekly meetings and a Kubernetes Slack channel.ko.build · read 5 Oct 2026
- Project status
- ko is a Cloud Native Computing Foundation Sandbox project.ko.build · read 5 Oct 2026
- Purpose
- ko is a simple, fast container image builder for Go applications.ko.build · read 5 Oct 2026
- Registry authentication
- ko supports registry credentials from Docker configuration and has built-in environment credential support for Google, Amazon, Azure, and GitHub container registries.ko.build · read 5 Oct 2026
