Validators
Dockerfile Validator
Validate your Dockerfile syntax and check against common best practices instantly. This tool provides real-time feedback and diagnostic messages to help you build more efficient and secure container images.
Validate your Dockerfile syntax and check against common best practices instantly. This tool provides real-time feedback and diagnostic messages to help you build more efficient and secure container images.
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Tip
Always specify a specific version tag for base images instead of using 'latest' to ensure reproducible builds.
Best Practice
Combine RUN commands and clean up package manager caches in the same layer to minimize image size.
FROM instruction to define the environment.ADD when COPY is preferred or misconfiguring ENTRYPOINT and CMD combinations.RUN), and file paths are case-sensitive.RUN instructions or missing backslashes in multi-line commands.Did You Know?
The .dockerignore file works similarly to .gitignore and prevents sensitive data from entering the Docker build context.
RUN commands using && to reduce the final image size.USER instruction to run applications with limited privileges for better security.Q: Why is my build failing even if the validator says it is okay? A: The validator checks syntax and best practices, but it cannot verify if external files in your build context or remote base images actually exist.
Q: Should I always use ADD or COPY? A: Use COPY for simple file transfers from the local context. Use ADD only when you need to fetch remote URLs or extract local tar files automatically.
Q: Does this validator support multi-stage builds? A: Yes, it recognizes multiple FROM instructions and validates aliases used in multi-stage Dockerfiles.
Tip
Use multi-stage builds to keep your final production images small by excluding build-time dependencies.