# aws-cloudformation/cfn-lint

CloudFormation Linter

Repository: https://github.com/aws-cloudformation/cfn-lint
Canonical: https://ross.abutalabs.com/products/cfn-lint
Language: Python
License: MIT-0
License Family: permissive
Topics: cloudformation, aws, aws-cloudformation, linter, cfn-lint
Last push: 2026-08-26T21:48:30+00:00

## Health v2 (maintenance only)
Score: 94/100 (v2, computed 2026-09-03T02:39:23.370411+00:00)
- activity 99, release rhythm 85, longevity 100
- inputs: {"age_days": 3067, "days_push": 7, "days_rel": 20, "gap_med": 5, "n_releases_24m": 120}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 2640, forks 640 (observed 2026-08-28T04:07:06.464256+00:00)

## What it is
cfn-lint is a Python CLI tool that validates AWS CloudFormation templates (YAML/JSON) against resource provider schemas and best-practice checks. It supports SAM template transformation and validates resource properties and values on a best-effort basis.

## Use cases
- validate cloudformation templates before deploying
- lint aws cloudformation yaml files in ci
- check cfn template resource properties and values
- validate aws sam templates
- catch cloudformation best practice violations
- verify cfn template syntax and schema compliance

## When to choose
- you write or review AWS CloudFormation or SAM templates
- you want automated template validation in CI/CD pipelines
- you need schema-based checks for CloudFormation resource properties

## When to avoid
- you use Terraform, Pulumi, or other non-CloudFormation IaC tools
- you need guaranteed validation of all intrinsic function value combinations, since value checks are best-effort

## Facets
- artifact type: cli-tool
- maturity: active
- function: linter, cli, developer-tools, yaml, json
- domain: infrastructure-as-code, cloud-computing, developer-tools
- platform: python, cli, cross-platform
- tags: aws, cloudformation, infrastructure-as-code, template-validation, sam, devops, command-line

## Member repositories
- aws-cloudformation/cfn-lint (main) score 94

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:07:06.464256+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T02:19:07.998963+00:00, confidence not recorded.
  - readme: https://github.com/aws-cloudformation/cfn-lint (fetched 2026-08-28T04:07:06.464256+00:00, sha 646c90df0fcc)
- Data as of 2026-08-30T08:39:29.467469+00:00.