---
title: "Dockerfile Checker | Free DevOps Tool | FOSSA"
description: "Free online Dockerfile validator and best practices checker. Analyze Dockerfiles for security issues, optimization opportunities, and best practices."
canonical_url: "https://fossa.com/resources/devops-tools/dockerfile-checker/"
markdown_url: "https://fossa.com/resources/devops-tools/dockerfile-checker.md"
language: "en"
author: "FOSSA"
organization: "FOSSA"
---

# Dockerfile Checker | Free DevOps Tool | FOSSA

> Free online Dockerfile validator and best practices checker. Analyze Dockerfiles for security issues, optimization opportunities, and best practices.

## Dockerfile Best Practices Checker

Analyze your Dockerfile for common anti-patterns and get recommendations for following best practices.

Score: \-/100

Paste a Dockerfile and click "Analyze Dockerfile" to check for best practices

### Dockerfile Best Practices

A well-crafted Dockerfile ensures that your containers are efficient, secure, and maintainable. Here are some best practices to follow when writing Dockerfiles:

#### Use Multi-stage Builds

Multi-stage builds allow you to use multiple FROM statements in your Dockerfile. This is useful for creating smaller production images by separating build-time dependencies from runtime dependencies.

```
FROM node:18 AS build
WORKDIR /app
COPY package*.json ./
RUN npm install
COPY . .
RUN npm run build

FROM node:18-alpine
WORKDIR /app
COPY --from=build /app/dist ./dist
CMD ["node", "dist/index.js"]
```

#### Minimize Layer Count and Size

- Group related commands in a single RUN instruction to reduce layers
- Clean up package manager caches in the same RUN instruction
- Use .dockerignore to exclude unnecessary files
- Choose smaller base images (e.g., alpine variants)

#### Security Best Practices

- Avoid running containers as root by using the USER instruction
- Set proper file permissions
- Never store secrets in the Dockerfile (use environment variables or secrets management)
- Scan images for vulnerabilities
- Use specific version tags instead of 'latest'

#### Additional Recommendations

- Use COPY instead of ADD for simple file copying
- Set WORKDIR instead of using RUN cd
- Use ENTRYPOINT with CMD for better container execution
- Include HEALTHCHECK instructions to monitor container health
- Sort multi-line arguments alphanumerically to avoid duplication

##### Pro Tip

For production containers, always use a non-root user, pin all dependency versions (including base images), and keep your container images as small as possible. This improves security, reproducibility, and performance.

### Get Started with FOSSA

Start managing your dependencies, licenses, and vulnerabilities today.

## Source

Canonical page: https://fossa.com/resources/devops-tools/dockerfile-checker/