dockerfile-optimizer

dockerfile-optimizer is a skill for Claude Code, Codex from sourav15mukherjee/skillforge-free-skills. It costs 63 tokens per session (1,146 once invoked), scanned A, original, MIT.

A guide for reviewing and improving Dockerfiles, which describe how to build container images. It examines image size, build-layer caching, security, build speed, dependency installation, and related files such as .dockerignore.

In plain words
What is it for?
Use it to optimize Docker builds, reduce image size, improve cache reuse, exclude build-only dependencies, harden container configuration, and review Docker-related setup.
Why use it?
Docker images may become unnecessarily large, slow to build, or include files and dependencies that should not be shipped. This identifies issues and proposes prioritized changes with before-and-after differences.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to optimize Docker builds, reduce image size, improve cache reuse, exclude build-only dependencies, harden container configuration, and review Docker-related setup.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/sourav15mukherjee/skillforge-free-skills/dockerfile-optimizer
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add sourav15mukherjee/skillforge-free-skills --skill dockerfile-optimizer
Clone the repo
git clone --depth 1 https://github.com/sourav15mukherjee/skillforge-free-skills

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for dockerfile-optimizer

README.md
[![agentmods](https://agentmods.dev/badge/skills/sourav15mukherjee/skillforge-free-skills/dockerfile-optimizer/github.svg)](https://agentmods.dev/skills/sourav15mukherjee/skillforge-free-skills/dockerfile-optimizer)
Your own site
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Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for dockerfile-optimizer

Your own site · 80×15
<a href="https://agentmods.dev/skills/sourav15mukherjee/skillforge-free-skills/dockerfile-optimizer"><img src="https://agentmods.dev/badge/skills/sourav15mukherjee/skillforge-free-skills/dockerfile-optimizer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 63 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,146 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00063 $0.01146
Opus 5 $0.00032 $0.00573
Sonnet 5 $0.00013 $0.00229
Haiku 4.5 $0.00006 $0.00115

Measured 10d ago against content hash 63ffaffacb27, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

dockerfile-optimizer scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 10d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

- Using ADD for remote URLs instead of RUN curl
dockerfile-optimizer/SKILL.md · 131 lines

How it starts

The opening of the file, as written. The whole thing — 131 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Dockerfile Optimizer

Analyze Dockerfiles across four dimensions and produce prioritized, actionable optimizations with estimated impact.

Workflow

  1. Locate and read the Dockerfile(s) Search for Dockerfile, Dockerfile.*, or *.dockerfile in the project. Read all found files. Also check for .dockerignore and docker-compose.yml for context.

  2. Pass 1 — Image Size Analysis Check for:

    • Using slim/alpine/distroless base images where appropriate
    • Combining RUN commands to reduce layers
    • Cleaning package manager caches (apt clean, apk --no-cache, pip --no-cache-dir)
    • Multi-stage build usage to exclude build dependencies
    • Unnecessary files copied into the image (check .dockerignore)
    • Using COPY instead of ADD (ADD has implicit tar extraction)
    • Installing only production dependencies (npm ci --omit=dev, pip install --no-dev) Score: 1-10. Estimate total size reduction in MB/GB.
  3. Pass 2 — Layer Caching Analysis Check for:

    • Ordering instructions from least to most frequently changing
    • Separate dependency install step before COPY . .
    • Using BuildKit cache mounts for package managers
    • Avoiding COPY . . before dependency installation
    • Using .dockerignore to prevent cache invalidation Score: 1-10. Estimate rebuild time improvement.
  4. Pass 3 — Security Hardening Check for:

    • Running as non-root user (USER directive)
    • Using specific image tags, not :latest
    • No secrets in ENV or ARG that leak into final image
    • No unnecessary ports exposed
    • Using read-only filesystem where possible
    • Scanning for known CVEs in base image
    • Dropping capabilities (CAP_DROP ALL)
    • Using HEALTHCHECK Score: 1-10. List specific vulnerabilities found.
  5. Pass 4 — Build Speed Check for:

    • BuildKit syntax enabled (# syntax=docker/dockerfile:1)
    • Parallel build stages where possible
    • Using --mount=type=cache for apt/pip/npm caches
    • Avoiding unnecessary .dockerignore exclusions that force full rebuilds
    • Using ADD for remote URLs instead of RUN curl Score: 1-10. Estimate build time savings.

Read the full file on GitHub · 131 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 10d ago First seen · 131 lines · 63 tokens per session scan A 63ffaffacb27

Subscribe to this mod's changes

dockerfile-optimizer is a skill published in the GitHub repository sourav15mukherjee/skillforge-free-skills (5 stars, last pushed 5mo ago), licensed MIT. It adds 63 tokens to every session and 1,146 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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