Does this build the image?

No, it only performs static analysis on the text you paste.

What issues are checked?

Base image pinning, USER, HEALTHCHECK, ADD vs COPY, apt/apk cache cleanup, exec form CMD/ENTRYPOINT, and more.

Is my Dockerfile uploaded anywhere?

No, everything runs locally in your browser.

Dockerfile Linter

Lint a Dockerfile for common best-practice issues.

Works Offline

Privacy First

No Login

No API

Dockerfile

Paste your Dockerfile contents

Findings

Static best-practice checks

Errors

Warnings

Info

L3 Copying the whole context (`COPY . .`) early can invalidate the Docker layer cache — copy dependency manifests first.
L5 Prefer exec form `CMD ["executable", "arg"]` over shell form for proper signal handling.
General No USER instruction found — the container will run as root by default.
General No HEALTHCHECK instruction — consider adding one for orchestrators to monitor container health.

About the Dockerfile Linter

Paste a Dockerfile and get instant feedback on common issues: unpinned base images, missing USER instruction, shell-form CMD/ENTRYPOINT, apt-get cache hygiene, and more.

Examples

Unpinned image

FROM node:latest

Output

Warning: avoid latest tag

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Frequently asked questions

Version 1.0.0 · Updated 2026-08-06 · Runs entirely in your browser