AWS CloudFormation Linter (cfn-lint)

cfn-lint is an open-source static analysis tool developed by AWS that checks CloudFormation templates (YAML/JSON) for potential errors, adherence to AWS best practices, and valid resource configurations. It validates templates against the AWS CloudFormation resource provider schemas and additional checks, aiming to catch issues before deployment. The project is actively maintained with frequent updates, often including new CloudFormation schemas and linting rules.