Online Tool Store
Dockerfile Builder
Assemble a Dockerfile with multi-stage builds, a non-root user, correct layer ordering, and a .dockerignore that keeps the image small.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Developer
Dockerfile Builder
Frontend preview — no upload or external service.
Dockerfile
Multi-stage Node build: dependencies installed in a builder stage, only production node_modules and built output copied into a slim runtime image running as an unprivileged user.
How the Dockerfile Builder works
- Choose the runtime and whether the build needs a compile step.
- Keep the dependency install above the source copy so the layer cache survives code changes.
- Copy the Dockerfile and the generated .dockerignore together — the ignore file is half the size saving.
The method
Docker caches each layer and invalidates every layer after the first change. Copying source before installing dependencies means every code edit reinstalls everything.
COPY package*.json → RUN install → COPY source keeps the install layer cached
Reversing those two lines is the single most common cause of slow rebuilds, and it costs minutes on every commit.
FAQ
Why run as a non-root user?
Because a process compromised inside the container is root inside it by default, which widens what an escape or a mounted volume exposes. Adding a user is two lines and removes a whole class of risk.
Why does layer order matter so much?
Docker invalidates the cache from the first changed layer onward. Installing dependencies before copying source keeps that expensive step cached across code changes.
Is .dockerignore really necessary?
Yes. Without it, the build context includes node_modules, .git and local artefacts, which slows every build and can leak files into the image.
How we compare
| Feature | Online Tool Store | A CLI script | An IDE plugin |
|---|---|---|---|
| Multi-stage by default | ✓ | If you write it | Yes |
| Non-root user included | ✓ | ✗ | Sometimes |
| Generates .dockerignore | ✓ | ✗ | ✗ |
| Explains layer caching | ✓ | ✗ | ✗ |
Dockerfile Builder gets layer order and the non-root user right by default — the two things hand-written Dockerfiles most often miss.