What are Custom Actions

Custom GitHub Actions empower you to tailor your CI/CD pipelines to meet project-specific requirements. While the GitHub Marketplace offers a wealth of community-maintained Actions—covering tasks like runtime setup, artifact transfer, Docker builds, test report syncing, and Kubernetes deployments—there are scenarios where you need:

Project-specific logic not covered by existing Actions
Integration with internal or legacy services
Complex orchestration with conditional steps or custom dependencies
Strict compliance or security policies requiring in-house solutions

Leverage community Actions whenever possible to reduce maintenance overhead. Create a custom Action only when you need functionality that isn’t already available.

Common use cases include:

Publishing an npm package when a new Git tag is created
Sending SMS or Slack alerts upon critical issue creation
Deploying custom security policies or infrastructure templates

GitHub supports three main Action types. You can compare their features below:

Action Type	Runner Support	Isolation	Best For
Composite Actions	Linux, macOS, Windows	Low (host)	Bundling repeated workflow steps
Docker Container	Linux only	High (container)	Complex environment or OS dependencies
JavaScript Actions	Linux, macOS, Windows	Medium	Fast, lightweight scripting tasks

Composite Actions

Composite Actions let you encapsulate multiple workflow steps into a single reusable unit.

# .github/actions/my-composite/action.yml
name: "My Composite Action"
description: "Install deps, run tests, and lint code"
runs:
  using: composite
  steps:
    - name: Checkout code
      uses: actions/checkout@v3
    - name: Install dependencies
      run: npm ci
    - name: Run tests
      run: npm test

Pros: Simplifies workflows, DRY principle, cross-platform
Cons: Can become hard to maintain if too many steps are bundled

Docker Container Actions

Container Actions run inside a Docker environment defined by you.

# .github/actions/my-docker/Dockerfile
FROM node:16
RUN npm install -g aws-cli
COPY entrypoint.sh /entrypoint.sh
ENTRYPOINT ["/entrypoint.sh"]

# .github/actions/my-docker/action.yml
name: "My Docker Action"
runs:
  using: docker
  image: Dockerfile
  args:
    - "--region"
    - "us-east-1"

Pros: Full OS control, consistent environment, ideal for complex dependencies
Cons: Linux only, requires Docker knowledge, startup overhead

Docker container Actions run exclusively on Linux runners. Make sure your workflow requirements align with Linux-only execution.

JavaScript Actions

JavaScript Actions execute directly on the runner via Node.js.

// .github/actions/my-js-action/index.js
import core from "@actions/core";

async function run() {
  try {
    const name = core.getInput("name");
    core.info(`Hello, ${name}!`);
  } catch (error) {
    core.setFailed(error.message);
  }
}

run();

# .github/actions/my-js-action/action.yml
name: "My JS Action"
runs:
  using: "node16"
  main: "index.js"
inputs:
  name:
    description: "Your name"
    required: true

Pros: Fast startup, cross-platform, simple scripting
Cons: Less isolated—be mindful of side effects on the host runner

Criteria	Composite	Docker Container	JavaScript
Speed	Fast	Moderate	Fastest
Isolation	Low	High	Medium
Cross-platform support	Yes	No	Yes
Maintenance overhead	Moderate	High	Low

Select the type that best aligns with your project’s needs—whether you prioritize simplicity, isolation, performance, or cross-platform support.

Introduction

GitHub Actions - Core Concepts

Continuous Integration with GitHub Actions

Continuous Deployment with GitHub Actions

Reusable Workflows and Reporting

Custom Actions

Self Hosted Runner

Security Guide

GitHub Actions in the Enterprise Cloud

What are Custom Actions

Composite Actions

Docker Container Actions

JavaScript Actions

Watch Video

​Composite Actions

​Docker Container Actions

​JavaScript Actions

Watch Video

Composite Actions

Docker Container Actions

JavaScript Actions