Jobs, Steps, and Actions

Jobs run on a runner; each job has steps that run commands or reusable actions.

Syntax

jobs:
  <id>:
    runs-on: ubuntu-latest
    steps:
      - uses: ...
      - run: ...

A job runs on a fresh runner (a virtual machine chosen with runs-on). By default jobs run in parallel; use needs to make one wait for another.

Steps

A job's steps run in order. A step is either:

run: — a shell command.
uses: — a reusable action from the Marketplace, like actions/checkout@v4.

Pass inputs to an action with a with: block.

Example

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: 20
      - run: npm ci
      - run: npm test

  deploy:
    needs: test        # wait for test to pass first
    runs-on: ubuntu-latest
    steps:
      - run: echo "Deploying..."

When to use it

A CI pipeline defines separate lint, test, and build jobs that run in parallel, cutting total run time in half.
A deploy job uses needs: [test] to ensure it only runs after the test job passes, preventing broken code from reaching production.
A developer uses a community action (actions/setup-python) as a step to install a specific Python version without writing installer scripts.

More examples

Two parallel jobs in one workflow

Two jobs with no dependency on each other run concurrently on separate runners, reducing total pipeline duration.

jobs:
  lint:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - run: npm run lint

  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - run: npm test

Sequential jobs using needs

The deploy job waits for the test job to succeed before starting, creating a safe linear pipeline.

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - run: npm test

  deploy:
    needs: test
    runs-on: ubuntu-latest
    steps:
      - run: ./scripts/deploy.sh

Use a marketplace action as a step

The setup-python action installs the requested Python version on the runner so the pytest step finds the correct interpreter.

steps:
  - uses: actions/checkout@v4
  - uses: actions/setup-python@v5
    with:
      python-version: '3.12'
  - run: python -m pytest tests/

Discussion

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