Preview Deployments (Deploy Previews) for Pull Requests

Preview Deployments Setup for Pull Requests

Preview Deployment — an automatically created temporary environment for each Pull Request with a unique URL like https://pr-123.preview.example.com. Reviewer opens a live site, clicks through the interface, checks changes without needing to clone the repo and set up local environment.

Platforms with Built-in Preview Deployments

Vercel — best option for Next.js and static sites. Preview deployments work out of the box when connecting GitHub repo. Each PR gets unique URL, link added to PR comment automatically.

Netlify — similar functionality for static sites and JAMstack. Deploy Previews enabled by default. Supports split testing between preview and production.

Railway / Render — for full-stack apps with database. Railway creates isolated environment with separate DB for each PR.

Custom Implementation on VPS

For apps that can't deploy to Vercel/Netlify (Docker containers, specific requirements):

# .github/workflows/preview.yml
name: Preview Deployment
on:
  pull_request:
    types: [opened, synchronize, reopened]

jobs:
  deploy-preview:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Build Docker image
        run: |
          docker build -t app:pr-${{ github.event.pull_request.number }} .

      - name: Deploy to preview server
        uses: appleboy/ssh-action@v1
        with:
          host: ${{ secrets.PREVIEW_SERVER_HOST }}
          username: deploy
          key: ${{ secrets.PREVIEW_SSH_KEY }}
          script: |
            docker pull registry.example.com/app:pr-${{ github.event.pull_request.number }}
            docker stop app-pr-${{ github.event.pull_request.number }} || true
            docker run -d --name app-pr-${{ github.event.pull_request.number }} \
              -p 0:3000 \
              --label traefik.enable=true \
              --label "traefik.http.routers.pr-${{ github.event.pull_request.number }}.rule=Host(\`pr-${{ github.event.pull_request.number }}.preview.example.com\`)" \
              registry.example.com/app:pr-${{ github.event.pull_request.number }}

      - name: Comment PR with preview URL
        uses: actions/github-script@v7
        with:
          script: |
            github.rest.issues.createComment({
              issue_number: context.issue.number,
              owner: context.repo.owner,
              repo: context.repo.repo,
              body: `Preview: https://pr-${context.issue.number}.preview.example.com`
            })

Traefik automatically routes traffic to the right container by subdomain. Wildcard DNS record *.preview.example.com points to preview server.

Cleanup of Outdated Environments

# Remove preview when PR closed
on:
  pull_request:
    types: [closed]

jobs:
  cleanup:
    runs-on: ubuntu-latest
    steps:
      - name: Remove preview deployment
        uses: appleboy/ssh-action@v1
        with:
          script: |
            docker stop app-pr-${{ github.event.pull_request.number }}
            docker rm app-pr-${{ github.event.pull_request.number }}

Database for Preview Environments

Options:

• Shared read-only database — fast, but can't test writes
• Separate DB per PR — full isolation, but requires resources. Neon (PostgreSQL) supports database branching: creates DB branch instantly via copy-on-write
• Seeded in-memory database — SQLite or PostgreSQL with fixed test data

Timeline

Preview Deployments on Vercel/Netlify — 0.5 day. Custom implementation with Docker, Traefik and cleanup — 2–3 days. Add database branching via Neon — 1 day.