cfn-lint vs kubeconform

cfn-lint is a free, open-source validator for AWS CloudFormation YAML and JSON templates. It checks templates against resource provider schemas and applies additional rules, including validation of property values and best practices. AWS Serverless Application Model templates are processed after transformation with AWS SAM. Users can configure built-in checks through command-line options, configuration files, or CloudFormation template metadata, and can add custom rules. Results can be emitted as quiet, parseable, JSON, JUnit, pretty, or SARIF output. Installation options documented by the project include pip, Homebrew for macOS, and Docker; supported Python versions are 3.10 through 3.14. Listed integrations include Atom, Emacs, NeoVim/Vim, Sublime, Visual Studio Code, IntelliJ IDEA, GitHub Actions, and pre-commit. The project treats complex template-value validation as best effort and does not fail merely because it cannot interpret or translate a value. The repository identifies its license as MIT No Attribution, and the plan costs nothing.

Kubeconform is a command-line tool for validating Kubernetes manifests before deployment. It checks files against Kubernetes OpenAPI specifications, helping catch configuration problems before they reach a cluster. Validation and schema downloads run concurrently, and downloaded files are cached in memory. By default, it uses a self-updating fork of the Kubernetes JSON schema registry to supply schemas for recent Kubernetes versions. For custom resources, users can point it to local or remote schemas; local schemas also make offline validation possible. Results can be produced as JSON, JUnit, TAP, or plain text. Documentation describes using its Docker images in GitHub Actions and GitLab CI, and the images are published to GitHub Container Registry. It is free, with a listed plan of free. Installation instructions cover Linux, macOS through Homebrew, and Windows. Its checks do not cover additional server-side validation, and its Go module interface is still work in progress and unstable.