Skip to main content
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:
The image is a comparison chart of three types of custom actions: Composite Actions, Docker Actions, and JavaScript Actions, highlighting their features and differences.
Action TypeRunner SupportIsolationBest For
Composite ActionsLinux, macOS, WindowsLow (host)Bundling repeated workflow steps
Docker ContainerLinux onlyHigh (container)Complex environment or OS dependencies
JavaScript ActionsLinux, macOS, WindowsMediumFast, 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
CriteriaCompositeDocker ContainerJavaScript
SpeedFastModerateFastest
IsolationLowHighMedium
Cross-platform supportYesNoYes
Maintenance overheadModerateHighLow
Select the type that best aligns with your project’s needs—whether you prioritize simplicity, isolation, performance, or cross-platform support.

Watch Video