Format Dockerfile Online — Instruction Normalizer

Normalize Dockerfile instruction casing and spacing with dockerfile-utils — browser-local formatting.

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Dockerfile input

Formatted Dockerfile

dockerfile-utils loads on demand — your Dockerfile never leaves the browser.

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Dockerfile formatter — instruction normalization

Turn lowercase or inconsistent Dockerfiles into readable, review-friendly instructions before opening a PR or sharing in docs.

Developer notes

• Loads dockerfile-utils on demand. • Normalizes instruction casing even when format returns no TextEdits. • Does not run Hadolint or ShellCheck. • Syntax errors may surface from the formatter validator.

When teams pick this route

• Normalize Dockerfiles copied from blog posts (often lowercase). • Prepare a Dockerfile snippet for internal style guides. • Quick format before lint-dockerfile for DL rules. • Clean up hand-edited multi-stage files.

Worked examples

Lowercase instructions from a tutorial

Before

from node:20-alpine
workdir /app
copy package*.json ./
run npm ci --omit=dev
copy . .
expose 3000
cmd ["npm", "start"]

After format

FROM node:20-alpine
WORKDIR /app
COPY package*.json ./
RUN npm ci --omit=dev
COPY . .
EXPOSE 3000
CMD ["npm", "start"]

Multi-stage build skeleton

Before

from golang:1.22 AS build
workdir /src
copy go.mod go.sum ./
run go build -o /bin/api ./cmd/api

from gcr.io/distroless/base
COPY --from=build /bin/api /api
entrypoint ["/api"]

After format

FROM golang:1.22 AS build
WORKDIR /src
COPY go.mod go.sum ./
RUN go build -o /bin/api ./cmd/api

FROM gcr.io/distroless/base
COPY --from=build /bin/api /api
ENTRYPOINT ["/api"]