Dockerfile Validator
Analyze your Dockerfile for best practices, security, and optimization.
Incolla o carica il tuo Dockerfile
Incolla il contenuto del Dockerfile o caricalo tramite il pannello sopra.
Incolla il contenuto del tuo Dockerfile o caricalo tramite il pannello di upload.
Come utilizzare Dockerfile Linter
Attach or load the Dockerfile
Attach the Dockerfile content to the editor, copy it into the designated area, or load from a file. Alternatively, try the problematic example or optimized example to see how it works immediately.
Start Analysis
Click on "Analyze": the engine applies 12 static rules (base image, layer, security, health check, multi-stage) directly in the browser, without sending content to any server.
Read scores, grades, and issues found
Get a grade from A to F, a numerical score and a list of issues divided by severity (error, warning, info), each with the relevant line and a correction suggestion.
Correct and recheck
Apply suggestions to the Dockerfile and retry analysis until a satisfactory grade (A or B) is reached. You can copy the full report with the dedicated button.
Suggerimenti
- Start with a good example (multi-stage, user non-root, healthcheck) to see how a Dockerfile should be structured.
- Correct errors first (blocking for grade), then warnings: consecutive RUNs and non-root USER usage are often the most impactful improvements on scores.
- Use "Copy Report" to save the complete list of issues and share it with code review or attach it to a tracking issue.
Domande frequenti
What rules does the Dockerfile Linter enforce?
Apply 12 static rules: initial FROM presence, avoid "latest" tags, consecutive RUNs to combine, avoid apt-get upgrades, missing --no-install-recommends, use ADD instead of COPY, no non-root USER, no HEALTHCHECK, no multi-stage builds, exposed SSH port 22, missing WORKDIR before COPY/RUN and .dockerignore reminders.
How is the grade from A to F calculated?
Every error deducts 20 points, every warning deducts 7 points and every info deducts 2 points from a score starting at 100. The resulting grade is A from 90 points up, B from 75, C from 55, D from 35, otherwise F. Errors of type "error" therefore have the greatest impact on the score.
Is my Dockerfile being sent to an external server?
No. Analysis is a pure TypeScript rule engine that runs entirely in the browser: the content of your Dockerfile never leaves your device and is not saved anywhere.
Why is it reported even if I don't have blocking errors?
Some rules are at the "info" level (e.g. dockerignore or multi-stage builds) and serve to improve image size and maintainability, not to report bugs. Focus on errors first, then warnings, last on information.
Does the tool replace hadolint or other Docker linters?
No, and it's a quick and free test based on 12 common rules thought for immediate feedback during writing. For CI/CD pipeline with more extended and configurable rules, it is recommended to accompany dedicated tools like Hadolint.