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GitHub Actions can react to a wide range of webhook events. This guide covers four key triggers—workflow_dispatch, repository_dispatch, workflow_call, and workflow_run—to help you automate and chain your CI/CD pipelines efficiently.
The image is a table listing various trigger events, with some highlighted in green and red, related to GitHub actions or workflows.
EventTrigger TypeUse Case
workflow_dispatchManualRun workflows on demand with custom inputs
repository_dispatchHTTP POSTIntegrate external services via API calls
workflow_callWorkflow reuseBuild modular, reusable pipelines
workflow_runWorkflow chainingChain workflows based on completion status

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1. workflow_dispatch

The workflow_dispatch event enables manual, on-demand execution of workflows. You can define custom inputs to parameterize each run: 
name: Manual Trigger Demo

on:
  workflow_dispatch:
    inputs:
      message:
        description: "Custom message to echo"
        required: false
        type: string

jobs:
  greet:
    runs-on: ubuntu-latest
    steps:
      - name: Echo input message
        run: echo "Message: ${{ github.event.inputs.message }}"
After pushing this file, go to the Actions tab, choose Manual Trigger Demo, click Run workflow, and provide a value for message.
If you omit required: true, the input becomes optional and can be left blank.

​
2. repository_dispatch

Use repository_dispatch to fire workflows from external systems via an HTTP POST: 
name: External API Trigger

on:
  repository_dispatch:
    types: [system_result]

jobs:
  report:
    runs-on: ubuntu-latest
    steps:
      - name: Display payload
        run: echo "Payload: ${{ github.event.client_payload.message }}"
Trigger it with: 
curl -X POST \
  -H "Accept: application/vnd.github+json" \
  -H "Authorization: Bearer $GITHUB_TOKEN" \
  https://api.github.com/repos/<owner>/<repo>/dispatches \
  -d '{
    "event_type": "system_result",
    "client_payload": {
      "message": "Error: API Timeout"
    }
  }'
Ensure your GITHUB_TOKEN has repo scope; otherwise the API request will fail with a 403 error.

​
3. workflow_call

The workflow_call event helps you define reusable workflows that other workflows can invoke. This promotes DRY principles across repositories: 
name: Reusable Workflow

on:
  workflow_call:
    inputs:
      message:
        description: "Text to echo"
        required: false
        type: string
    secrets:
      MY_SECRET:
        required: true

jobs:
  echo-job:
    runs-on: ubuntu-latest
    steps:
      - name: Show inputs and secrets
        run: |
          echo "Msg: ${{ inputs.message }}"
          echo "Secret: ${{ secrets.MY_SECRET }}"
Invoke it from another workflow: 
jobs:
  call-reusable:
    uses: owner/repo/.github/workflows/reusable.yml@main
    with:
      message: "Hello from parent"
    secrets:
      MY_SECRET: ${{ secrets.MY_SECRET }}
Reusable workflows accept with and secrets inputs, making them highly parameterized and secure.

​
4. workflow_run

Chain workflows by listening to the completion of another workflow. For example, deploy only after a successful build:

​
Build Workflow

name: BUILD_WORKFLOW_DEMO

on:
  push:

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - run: echo "Build completed successfully"

​
Deployment Workflow

name: DEPLOY_WORKFLOW_DEMO

on:
  workflow_run:
    workflows:
      - BUILD_WORKFLOW_DEMO
    types:
      - completed

jobs:
  on-success:
    if: ${{ github.event.workflow_run.conclusion == 'success' }}
    runs-on: ubuntu-latest
    steps:
      - run: echo "Starting deployment steps..."

  on-failure:
    if: ${{ github.event.workflow_run.conclusion == 'failure' }}
    runs-on: ubuntu-latest
    steps:
      - run: echo "Build failed; skipping deployment."
You can filter on types (completed, requested, in_progress) and branch logic using ${{ github.event.workflow_run.conclusion }}.

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