> ## 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

> This article explains how to create and use custom GitHub Actions to enhance CI/CD pipelines with tailored scripts and containers.

Custom GitHub Actions empower you to extend and tailor your CI/CD pipelines beyond the capabilities of community-contributed workflows. By writing your own scripts or containers, you gain full control over specialized tasks, security requirements, and conditional logic.

## Why Create Custom Actions?

While the [GitHub Marketplace](https://github.com/marketplace?type=actions) offers a wealth of ready-made solutions—ranging from runtime setup and artifact transfers to Docker builds and Kubernetes deployments—you may still encounter gaps:

* Your project relies on proprietary or legacy systems that public actions don’t support.
* You need to orchestrate multi-step workflows with intricate conditional logic.
* Company policies mandate in-house code for security or compliance reasons.
* Existing actions lack the exact configurations or dependencies your build requires.

Custom actions bridge those gaps, giving you flexibility, reproducibility, and tighter integration with internal tools.

## Types of Custom Actions

GitHub supports three primary action types. The table below offers a quick comparison:

| Action Type              | Runner Support          | Ideal Use Case                                  |
| ------------------------ | ----------------------- | ----------------------------------------------- |
| Composite Actions        | Linux · macOS · Windows | DRY workflows by grouping steps into one action |
| Docker Container Actions | Linux only              | Full OS control & custom dependencies           |
| JavaScript Actions       | Linux · macOS · Windows | Fast startup & lightweight Node.js scripts      |

### Composite Actions

Composite actions let you bundle multiple workflow steps into a single, reusable action. They simplify your `workflow.yml` and promote consistency across repositories.

* Benefits
  * Encourages reuse and reduces duplication (DRY).
  * No extra runtime environment required.
* Considerations
  * Managing complex step dependencies can increase maintenance overhead.

<Callout icon="lightbulb" color="#1CB2FE">
  Use composite actions to encapsulate common setup tasks, such as linting or test orchestration, across multiple repositories.
</Callout>

### Docker Container Actions

Docker container actions run a customized container image defined by your `Dockerfile`. This isolates dependencies and environment configurations.

* Pros
  * Complete control over OS, libraries, and tools.
  * Ideal for builds requiring non-standard system packages.
* Cons
  * Adds Docker build and maintenance complexity.
  * Slower startup due to container initialization.

<Callout icon="triangle-alert" color="#FF6B6B">
  Docker container actions are supported **only** on Linux runners. Ensure your workflows target the correct OS.
</Callout>

### JavaScript Actions

JavaScript (or TypeScript) actions leverage Node.js and the [@actions/\*](https://github.com/actions/toolkit) toolkit. They run directly on the runner machine for fast initialization.

* Advantages
  * Cross-platform support (Linux, macOS, Windows).
  * Quick startup and lightweight—perfect for simple I/O tasks.
* Trade-offs
  * Less isolation compared to Docker; processes share the host environment.
  * Node.js runtime dependency.

<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/v1752876608/notes-assets/images/GitHub-Actions-What-are-Custom-Actions/custom-actions-comparison-chart.jpg)
</Frame>

## Choosing the Right Action

1. **Simple Script vs. Complex Environment**\
   – Use JavaScript actions for quick file operations or API calls.\
   – Opt for Docker containers when you need specialized system libraries.

2. **Cross-Platform Requirements**\
   – Composite and JavaScript actions both support macOS and Windows.\
   – Docker actions run exclusively on Linux.

3. **Maintenance and Reusability**\
   – Composite actions offer the best balance for grouping common steps.\
   – JavaScript actions scale well for small utility tasks without container overhead.

## References

* [GitHub Actions Documentation](https://docs.github.com/en/actions)
* [GitHub Marketplace – Actions](https://github.com/marketplace?type=actions)
* [Actions Toolkit for JavaScript](https://github.com/actions/toolkit)

<CardGroup>
  <Card title="Watch Video" icon="video" cta="Learn more" href="https://learn.kodekloud.com/user/courses/github-actions/module/cdb7c2b7-442d-440c-a4f1-d6679733ffd8/lesson/22b27d45-aa89-4e42-9331-044bdab63ccf" />
</CardGroup>