Creating a composite action

In this guide, you'll learn how to build a composite action.


In this guide, you'll learn about the basic components needed to create and use a packaged composite action. To focus this guide on the components needed to package the action, the functionality of the action's code is minimal. The action prints "Hello World" and then "Goodbye", or if you provide a custom name, it prints "Hello [who-to-greet]" and then "Goodbye". The action also maps a random number to the random-number output variable, and runs a script named

Once you complete this project, you should understand how to build your own composite action and test it in a workflow.

Warning: When creating workflows and actions, you should always consider whether your code might execute untrusted input from possible attackers. Certain contexts should be treated as untrusted input, as an attacker could insert their own malicious content. For more information, see "Understanding the risk of script injections."


Before you begin, you'll create a repository on

  1. Create a new public repository on You can choose any repository name, or use the following hello-world-composite-action example. You can add these files after your project has been pushed to GitHub. For more information, see "Create a new repository."

  2. Clone your repository to your computer. For more information, see "Cloning a repository."

  3. From your terminal, change directories into your new repository.

    cd hello-world-composite-action
  4. In the hello-world-composite-action repository, create a new file called, and add the following example code:

    echo "Goodbye"
  5. From your terminal, make executable.

    chmod +x
  6. From your terminal, check in your file.

    git add
    git commit -m "Add goodbye script"
    git push

Creating an action metadata file

  1. In the hello-world-composite-action repository, create a new file called action.yml and add the following example code. For more information about this syntax, see "runs for a composite actions".


    name: 'Hello World'
    description: 'Greet someone'
      who-to-greet:  # id of input
        description: 'Who to greet'
        required: true
        default: 'World'
        description: "Random number"
        value: ${{ steps.random-number-generator.outputs.random-id }}
      using: "composite"
        - run: echo Hello ${{ inputs.who-to-greet }}.
          shell: bash
        - id: random-number-generator
          run: echo "::set-output name=random-id::$(echo $RANDOM)"
          shell: bash
        - run: ${{ github.action_path }}/
          shell: bash

    This file defines the who-to-greet input, maps the random generated number to the random-number output variable, and runs the script. It also tells the runner how to execute the composite action.

    For more information about managing outputs, see "outputs for a composite action".

    For more information about how to use github.action_path, see "github context".

  2. From your terminal, check in your action.yml file.

    git add action.yml
    git commit -m "Add action"
    git push
  3. From your terminal, add a tag. This example uses a tag called v1. For more information, see "About actions."

    git tag -a -m "Description of this release" v1
    git push --follow-tags

Testing out your action in a workflow

The following workflow code uses the completed hello world action that you made in "Creating an action metadata file".

Copy the workflow code into a .github/workflows/main.yml file in another repository, but replace actions/hello-world-composite-action@v1 with the repository and tag you created. You can also replace the who-to-greet input with your name.


on: [push]

    runs-on: ubuntu-latest
    name: A job to say hello
      - uses: actions/checkout@v2
      - id: foo
        uses: actions/hello-world-composite-action@v1
          who-to-greet: 'Mona the Octocat'
      - run: echo random-number ${{ }}
        shell: bash

From your repository, click the Actions tab, and select the latest workflow run. The output should include: "Hello Mona the Octocat", the result of the "Goodbye" script, and a random number.

Did this doc help you?

Privacy policy

Help us make these docs great!

All GitHub docs are open source. See something that's wrong or unclear? Submit a pull request.

Make a contribution

Or, learn how to contribute.