Do I need Docker installed?

No. Analysis is purely static and runs on the pasted text alone.

Which rules are checked?

More than 30 rules that mirror Hadolint v2.15 (DL4000, DL3007, DL3025, DL3057 and others) plus the platform extension BP001 for .dockerignore.

How do I hide informational findings?

Set Minimum severity shown to “Warnings and errors only” or “Errors only”.

Can I suppress a rule on one line?

Yes. Add a comment # hadolint ignore=DLxxxx (or a comma-separated list) on the instruction.

Is the HEALTHCHECK check always on?

It is enabled by default but can be turned off with the checkbox if a missing HEALTHCHECK should be ignored.

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Dockerfile Linter & Best-Practices Checker

Hadolint-style static analysis for Dockerfiles without a Docker daemon: 30+ rules across image pinning, package-manager hygiene, layer caching, secrets and signal handling, with severities, line numbers and fix examples.

Details

What this tool helps you do

Rule IDs and severities mirror Hadolint v2.15 (DL4000 MAINTAINER=error, DL3025 shell-form CMD=warning, DL3057 HEALTHCHECK=info/optional). The parser handles the # escape= directive, line continuations, BuildKit heredocs, JSON-array form, multi-stage state resets per FROM, and # hadolint ignore=DLxxxx suppressions. BP001 is a platform best-practice extension reminding about .dockerignore on whole-context COPY.

Execution

Run this tool

Fill in the form, run the tool, and review the result in one place.

Prepared example runs

Click an example to fill the form automatically. File inputs still need an upload.

2 examples

Lint a Dockerfile full of classic anti-patterns

FROM :latest, MAINTAINER, apt-get without cleanup, sudo + cd, ADD for a plain file, COPY . . without .dockerignore, a secret in ENV, EXPOSE 70000, shell-form CMD and USER root — every category fires with line numbers and fixes.

<section class="dfl">16 findings: 4 errors (DL4000, DL3004, DL3020, DL3011) · 8 warnings (DL3007, DL3008, DL4001, DL3003, DL3045, DL3064, DL3025, DL3002) · 4 info</section>

Multi-stage production build passes with a single advisory

A pinned multi-stage Node build (npm ci, COPY --from=build, non-root USER, JSON CMD, HEALTHCHECK) lints clean of errors and warnings — only the COPY . . .dockerignore advisory remains.

<section class="dfl">0 errors · 0 warnings · multi-stage (build → runtime) · non-root USER node</section>

Inputs

Set the required fields, then run the tool.

3 options

ContentPaste or type the main input values.1

Dockerfile contenttextareaRequired

SettingsAdjust formats, ranges, numbers, and modes.1

Minimum severity shownselectOptional

TogglesEnable or disable optional behavior.1

Include HEALTHCHECK rule (DL3057)checkboxOptionalEnabled when checked

Result

Ready for a run

Run the tool to preview files, text, structured data, or streamed output here.

Samples

Dockerfile Linter & Best-Practices Checker

What this tool helps you do

Run this tool

Prepared example runs

Inputs

Result

Examples that match this tool

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Prepared example runs

Inputs

Result

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Overview

When to use

How it works

Use cases

Examples

1. Lint a Dockerfile full of classic anti-patterns

2. Multi-stage production Node build

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