How to Deploy a Preview Environment Per PR in GitHub Actions

Reviewers move faster when every PR ships a live preview they can click, scoped to that PR alone.

Trigger on pull_request, derive a per-PR slug from the PR number, deploy to that namespace, and comment the URL.

Steps

• Trigger the workflow on pull_request (opened, synchronize, reopened).
• Build a unique environment name like pr-<number>.
• Deploy your app to that namespace or subdomain.
• Post the preview URL back to the PR.

Workflow

on:
  pull_request:
    types: [opened, synchronize, reopened]
jobs:
  preview:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - name: Deploy preview
        run: ./deploy.sh "pr-${{ github.event.number }}"
      - uses: marocchino/sticky-pull-request-comment@v2
        with:
          header: preview
          message: |
            Preview ready: https://pr-${{ github.event.number }}.preview.example.com

Gotchas

• Always pair this with a teardown on PR close or previews pile up and cost money.
• A sticky comment avoids spamming the PR with a new comment on every push.
• Latchkey runs preview deploys on cheaper runners and retries if a deploy step hits a transient error.

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