Generate a production-ready Dockerfile from a form: multi-stage builds, non-root user, healthcheck, ENV and labels. Templates for Python, Node, Go, Java.
This Dockerfile generator builds a complete, working Dockerfile from a form — pick a language, choose a base image, list your build commands, set the port and start command, and the file assembles itself live in the pane beside you. Copy it or download it as Dockerfile and it is ready to use. Everything runs in your browser; no project files are uploaded and nothing is stored.
It is aimed at the developer who knows what their application needs but does not want to re-derive Dockerfile syntax from memory for the fourth time this quarter, and at teams standardising how services get containerised. Seven quick-start templates cover the common cases — Python FastAPI, Python Django, Node.js Express, Next.js, Go API, static site on Nginx, and Java Spring Boot — each pre-filled with a sensible base image, the right dependency-install commands, the conventional port, and a correct CMD.
scratch for a static binary.builder stage and a separate runtime stage, with the appropriate COPY --from=builder lines for your language.COPY and RUN lines, editable and reorderable, with your own custom instructions added to the list.USER instruction.HEALTHCHECK with sensible interval, timeout, start-period, and retry values.LABEL, ENV, and ARG instructions.["node", "index.js"], not node index.js — so your process receives signals directly.docker build -t myapp ., then docker run -p 8000:8000 myapp.Docker caches each instruction as a layer and reuses it until something changes; once one layer is invalidated, every layer after it rebuilds. This is why the templates copy the dependency manifest on its own before copying the rest of the source:
COPY requirements.txt . → RUN pip install --no-cache-dir -r requirements.txt → COPY . .
Written that way, editing application code invalidates only the final COPY, and the dependency install — the slow step — comes straight from cache. Written as a single COPY . . followed by the install, every one-character change re-downloads every dependency. The same principle applies to COPY package*.json ./ before npm ci, and COPY go.* ./ before go mod download.
Two related habits: use npm ci rather than npm install so the lockfile is authoritative and the build is reproducible, and use pip install --no-cache-dir so pip’s download cache does not end up baked into the image.
A multi-stage build compiles in one image and ships in another, so the compiler, headers, and build dependencies never reach production. The Go template shows the pattern at its most extreme:
FROM golang:1.22-alpine AS builder, then COPY go.* ./, RUN go mod download, COPY . ., RUN CGO_ENABLED=0 go build -o /app/server .COPY --from=builder /app/server /app/serverCGO_ENABLED=0 is doing real work there: it produces a statically linked binary with no libc dependency, which is what makes running on scratch or a distroless base possible. The result is a few megabytes instead of the roughly 250MB build image.
The same logic applies elsewhere. Java builds with the JDK and runs on the JRE — eclipse-temurin:21-jdk-alpine to build, 21-jre-alpine to run. Front-end projects build with Node and serve the static output from nginx:alpine, which is around 40MB. Smaller images are not only cheaper to store and faster to pull; they contain fewer packages, which means fewer CVEs for your scanner to report.
By default a container process runs as root, and that root is the same UID 0 as on the host. If a process is compromised and a kernel or runtime flaw allows escape, that inherited privilege matters. Running as an unprivileged user is the single highest-value line in most Dockerfiles, which is why the generator emits it by default.
Three more practices worth adopting:
python:3.12-slim moves. For reproducible builds, pin by digest (python:3.12-slim@sha256:…) and update deliberately rather than accidentally.ENV and ARG values are visible in the image history to anyone who can pull it, and deleting a file in a later layer does not remove it from earlier ones. Inject secrets at runtime, or use BuildKit secret mounts..dockerignore. It is a separate file the generator does not produce, but without it COPY . . sweeps in .git, node_modules, local .env files, and build artefacts — bloating the image and leaking credentials. At minimum exclude .git, node_modules, .env*, and your virtualenv directory.Once the image builds, inventory what is inside it. The SBOM Generator produces a CycloneDX or SPDX bill of materials for the dependency set you just containerised.
Yes, free and with no signup. Generation happens in your browser — no project details are transmitted or stored.
Python, Node.js, Go, Rust, Java, .NET, and Nginx, each with a shortlist of recommended tags. Seven quick-start templates cover FastAPI, Django, Express, Next.js, a Go API, a static Nginx site, and Spring Boot.
Slim is the safer default. Alpine images are considerably smaller but use musl instead of glibc, which breaks some prebuilt Python wheels and native Node modules and can produce surprising DNS and timing behaviour. Choose Alpine when you have verified your dependencies work on it.
ENTRYPOINT defines the executable that always runs; CMD supplies default arguments, and anything you append to docker run replaces them. With only CMD set, the whole command is overridable — which is usually what you want for an application container.
The exec form, CMD ["node", "index.js"], runs your process as PID 1 directly. The shell form wraps it in /bin/sh -c, which swallows SIGTERM — so your application never gets a chance to shut down cleanly and the runtime kills it after the grace period.
The emitted snippet uses the BusyBox form (addgroup -g 1001 -S appgroup && adduser -u 1001 -S appuser -G appgroup), which is what Alpine provides. On Debian-based slim images use the shadow-utils equivalent instead: groupadd -g 1001 appgroup && useradd -u 1001 -g appgroup -m appuser. Also check that any directory your app writes to is owned by that user.
Whenever building requires tools that running does not — compilers, SDKs, bundlers, test dependencies. For an interpreted app with no build step it adds little. For Go, Rust, Java, .NET, or any bundled front end it typically cuts image size by an order of magnitude.
Not through ARG or ENV — both persist in image metadata and history. Use BuildKit’s --mount=type=secret for build-time credentials, and supply runtime configuration through environment variables set by your orchestrator or a secrets manager.
No, it produces the Dockerfile only. Write the .dockerignore yourself — it is short and it matters. If your deployment is described in YAML, the YAML to JSON Converter is useful for inspecting or transforming Compose and Kubernetes manifests.
Usually the build context or an intermediate layer. Check for a missing .dockerignore, package-manager caches left in place, and files deleted in a later layer that still occupy space in an earlier one. Run docker history on the image to see which instruction is responsible.
For the rest of the container workflow, use the YAML to JSON Converter for Compose and Kubernetes manifests, the JSON Validator & Formatter for config and registry payloads, and the SBOM Generator to document what ended up inside the image.
A Dockerfile is a text file containing sequential instructions that Docker uses to build a container image. Each instruction creates a layer in the image, and Docker caches layers to speed up subsequent builds. Dockerfiles define the operating system base, application dependencies, source code, configuration, and startup commands for containerized applications.
Writing efficient, secure Dockerfiles is a core DevOps skill. Poorly constructed Dockerfiles produce bloated images with security vulnerabilities, slow build times, and runtime issues. This tool generates Dockerfiles following current best practices for common application stacks.
| Instruction | Purpose | Example |
|---|---|---|
| FROM | Set the base image | FROM node:20-alpine |
| WORKDIR | Set the working directory | WORKDIR /app |
| COPY | Copy files from build context | COPY package*.json ./ |
| RUN | Execute commands during build | RUN npm ci --production |
| ENV | Set environment variables | ENV NODE_ENV=production |
| EXPOSE | Document the container port | EXPOSE 3000 |
| USER | Set the runtime user | USER node |
| CMD | Default runtime command | CMD ["node", "server.js"] |
| ENTRYPOINT | Fixed runtime executable | ENTRYPOINT ["python"] |
| HEALTHCHECK | Define health check | HEALTHCHECK CMD curl -f http://localhost/ |
Multi-stage builds use multiple FROM statements to separate build and runtime stages. Build dependencies stay in build stages, while only runtime artifacts go into the final image. This dramatically reduces image size and attack surface.
Running as root inside containers is a security risk. If an attacker escapes the container, they have root access to the host. Create a non-root user with USER directive and ensure the app has appropriate file permissions.
Use Alpine or distroless base images, multi-stage builds, .dockerignore to exclude unnecessary files, combine RUN commands to reduce layers, and remove package manager caches (apt-get clean, rm -rf /var/lib/apt/lists/*).
HEALTHCHECK instructions let Docker monitor container health. Example: HEALTHCHECK --interval=30s CMD curl -f http://localhost/ || exit 1. Orchestrators like Kubernetes use this to restart unhealthy containers.