For developers and DevOps engineers containerising an app. Pick your stack to get a production-ready Dockerfile and .dockerignore, or paste your own file to find the common mistakes.
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You enter
Node.js 22, port 3000, start command node server.js, multi-stage, non-root user and health check on; then the sample file to lint
The tool shows
A two-stage Dockerfile (npm ci --omit=dev, USER node, EXPOSE 3000, HEALTHCHECK, CMD ["node","server.js"]) with no lint warnings; the sample file gets 2 errors (apt-get update alone, a password in ENV), 2 warnings (:latest, runs as root) and 7 tips
It builds the app in one stage with all the build tools, then copies only the result into a small final image. The image is smaller, faster to pull and has less to attack.
If someone breaks into the app, root inside the container makes it much easier to harm the host. A USER line with a normal user limits the damage.
No. It checks the most common mistakes in your browser. For CI, also run a full linter such as hadolint and an image scanner.
Yes. It is free, needs no sign-up and runs entirely in your browser, so what you type is not uploaded. You only sign in if you want to email a result to yourself or save it to your CareerByteCode profile.
