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Dockerfile Validator
Validate your Dockerfile for syntax errors, security issues, and best practices. Checks instructions, image tags, layer optimization, and more.
About Dockerfile Validation
A Dockerfile is a text document containing instructions to assemble a Docker container image. Each instruction creates a layer in the image.
What we check:
- Valid Dockerfile instructions (FROM, RUN, COPY, etc.)
- FROM requirements — must be first instruction, image tag pinning
- Multi-stage build validation — stage names and
COPY --fromreferences - Security — running as root, piping scripts from URLs
- Best practices — ADD vs COPY, exec form vs shell form, apt-get cleanup
- Layer optimization — combining apt-get update and install, cleaning caches
- Deprecated instructions like
MAINTAINER - EXPOSE port validation and WORKDIR absolute paths
- HEALTHCHECK and USER instruction presence
Everything runs in your browser — no data is sent over the network.