> ## Documentation Index
> Fetch the complete documentation index at: https://notes.kodekloud.com/llms.txt
> Use this file to discover all available pages before exploring further.

# What are Custom Actions

> Custom GitHub Actions allow you to customize CI/CD pipelines for specific project needs beyond existing marketplace options.

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

<Callout icon="lightbulb" color="#1CB2FE">
  Leverage community Actions whenever possible to reduce maintenance overhead. Create a custom Action only when you need functionality that isn’t already available.
</Callout>

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:

<Frame>
  ![The image is a comparison chart of three types of custom actions: Composite Actions, Docker Actions, and JavaScript Actions, highlighting their features and differences.](https://kodekloud.com/kk-media/image/upload/v1752876097/notes-assets/images/GitHub-Actions-Certification-What-are-Custom-Actions/custom-actions-comparison-chart.jpg)
</Frame>

| 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.

```yaml theme={null}
# .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.

```dockerfile theme={null}
# .github/actions/my-docker/Dockerfile
FROM node:16
RUN npm install -g aws-cli
COPY entrypoint.sh /entrypoint.sh
ENTRYPOINT ["/entrypoint.sh"]
```

```yaml theme={null}
# .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

<Callout icon="triangle-alert" color="#FF6B6B">
  Docker container Actions run exclusively on Linux runners. Make sure your workflow requirements align with Linux-only execution.
</Callout>

## JavaScript Actions

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

```javascript theme={null}
// .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();
```

```yaml theme={null}
# .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.

* [GitHub Actions Documentation](https://docs.github.com/actions)
* [Creating a composite run steps action](https://docs.github.com/actions/creating-actions/creating-a-composite-run-steps-action)
* [Docker container actions](https://docs.github.com/actions/creating-actions/creating-a-docker-container-action)
* [JavaScript actions](https://docs.github.com/actions/creating-actions/creating-a-javascript-action)

<CardGroup>
  <Card title="Watch Video" icon="video" cta="Learn more" href="https://learn.kodekloud.com/user/courses/github-actions-certification/module/428391ee-45d0-4e9c-9e06-78d0c5ff7657/lesson/171274e9-ecd7-42a2-8206-53fd50b9c0cc" />
</CardGroup>