A Dockerfile that “just works” can still be quietly bloated, unreproducible, or running as root. This tool runs a quick static pass over common anti-patterns before you reach for a full build-and-scan cycle.
What Is the Dockerfile Linter?
The Dockerfile Linter checks a pasted Dockerfile against a set of common best-practice rules: unpinned or :latest base images, ADD used where COPY would do, unmerged apt-get update/install layers, missing non-root USER, risky curl | sh patterns, npm install where npm ci would be more reproducible, and missed multi-stage build opportunities.
How to Use It
- Open the tool at /tools/dockerfile-linter.
- Paste your Dockerfile content.
- Review the findings list, grouped by severity (error, warning, suggestion).
- Fix flagged lines and watch the findings update live.
Key Features
- Line-numbered findings so you can jump straight to the issue.
- Severity levels distinguishing real risks (like
curl | sh) from lower-priority suggestions. - Multi-stage build detection — flags single-stage Dockerfiles that install build tooling not needed at runtime.
- Fully static and offline — it doesn’t build the image or scan it for vulnerabilities.
When to Use This Tool
- Reviewing a Dockerfile in a pull request for common anti-patterns.
- Learning Docker best practices by seeing why a pattern is flagged.
- A quick first pass before running a more thorough tool like Hadolint in CI.
Try It Now
Open Dockerfile Linter directly, or press ⌘K and type the tool name from anywhere on the site.
Part of the DevOps Tools collection on WebdevToolbox — free, browser-based developer tools with no login required.