Free Developer Tool
Dockerfile Analyzer
Paste your Dockerfile and get an instant security and performance grade with actionable findings and a suggested optimized version. 100% Browser-Based
Findings
Security
Performance & Caching
Best Practices
Excellent Dockerfile!
No issues found. Your Dockerfile follows best practices.
Suggested Optimized Dockerfile
Best-effort suggestions based on detected issues. Review carefully before using in production.
How the Analyzer Works
1. Paste Your Dockerfile
Paste any Dockerfile — from a simple single-stage build to a complex multi-stage production image. Use "Load Example" to try it out instantly.
2. Get Scored & Graded
The analyzer checks 15+ rules across Security, Performance, and Best Practices. Each finding deducts points (HIGH=15, MED=8, LOW=3) from a score of 100.
3. Review the Fixes
Each finding includes a description and remediation snippet. The Optimized Dockerfile preview applies best-effort fixes automatically.
Dockerfile Best Practices
Never Run as Root
Containers running as root give attackers full host access if they escape. Always add a
USER instruction
with a non-root user. Create it with
RUN addgroup && adduser first.
Pin Image Tags
FROM node:latest is a
moving target — it changes with every upstream release, breaking your builds silently. Pin to a specific
version like FROM node:20-alpine for reproducibility.
Leverage Layer Caching
Docker caches each layer. Copy dependency manifests (package.json,
requirements.txt) and install
dependencies before copying your application code. This avoids re-installing on every code change.
Use Multi-Stage Builds
Multi-stage builds dramatically reduce final image size by separating build tools from the runtime image.
Use COPY --from=builder
to pull only compiled artifacts into a lean final stage.
Instruction Quick Reference
| Instruction | Purpose | Best Practice |
|---|---|---|
| FROM | Base image | Pin exact version; prefer alpine variants |
| RUN | Execute commands | Chain with && and clean up in same layer |
| COPY | Copy local files | Prefer over ADD; copy deps manifest first |
| ADD | Copy + extract/fetch | Avoid — use COPY unless you need tarball extract |
| USER | Set running user | Always set a non-root user before CMD/ENTRYPOINT |
| WORKDIR | Set working directory | Always set explicitly; use absolute paths |
| HEALTHCHECK | Container health probe | Add for orchestrators (Kubernetes, ECS) to detect failures |
| EXPOSE | Document ports | Informational only; document all ports the app uses |
When to Use This Tool
Code Reviews
Catch Dockerfile issues before they reach production. Run the analyzer as part of your PR review checklist to maintain consistent standards across the team.
Security Audits
Identify root container risks, exposed secrets in ENV/ARG, and unsafe ADD instructions that could introduce unexpected behavior in your container images.
Optimization
Reduce image build times and final image sizes by finding layer cache-busting patterns, unconsolidated RUN commands, and opportunities for multi-stage builds.
Need Docker & Container Expertise?
From Dockerfile optimization to full Kubernetes deployments — we design, build, and maintain containerized applications and CI/CD pipelines that scale. Let us bring your infrastructure up to production standards.
Talk to Our Team