How can I use CircleCI with Vercel?

You can use Vercel with CircleCI as your CI/CD provider to generate Preview Deployments for every git push and deploy to Production when code is merged into the main branch.

This approach is useful for developers who want full control over their CI/CD pipeline, or those who can't leverage Vercel's built-in git integration. This guide will help you get started using CircleCI with Vercel.

You can build your application locally (or in CircleCI) without giving Vercel access to the source code through vercel build. Vercel automatically detects your frontend framework and generates a .vercel/output folder conforming to the Build Output API specification.

vercel build allows you to build your project within your own CI setup, whether it be CircleCI or your own in-house CI, and upload only those build artifacts (and not the source code) to Vercel to create a deployment.

vercel deploy --prebuilt skips the build step on Vercel and uploads the previously generated .vercel/output folder from CircleCI. Let's define our jobs in .circleci/config.yml:

version: 2.1
jobs:
  preview_deployment:
    docker:
      - image: circleci/node:latest
    environment:
      VERCEL_ORG_ID: $VERCEL_ORG_ID
      VERCEL_PROJECT_ID: $VERCEL_PROJECT_ID
    steps:
      - checkout
      - run:
          name: Install Vercel CLI
          command: npm install --global vercel@latest
      - run:
          name: Pull Vercel Environment Information
          command: vercel pull --yes --environment=preview --token=$VERCEL_TOKEN
      - run:
          name: Build Project Artifacts
          command: vercel build --token=$VERCEL_TOKEN
      - run:
          name: Deploy Project Artifacts to Vercel
          command: vercel deploy --prebuilt --token=$VERCEL_TOKEN

  production_deployment:
    docker:
      - image: circleci/node:latest
    environment:
      VERCEL_ORG_ID: $VERCEL_ORG_ID
      VERCEL_PROJECT_ID: $VERCEL_PROJECT_ID
    steps:
      - checkout
      - run:
          name: Install Vercel CLI
          command: npm install --global vercel@latest
      - run:
          name: Pull Vercel Environment Information
          command: vercel pull --yes --environment=production --token=$VERCEL_TOKEN
      - run:
          name: Build Project Artifacts
          command: vercel build --prod --token=$VERCEL_TOKEN
      - run:
          name: Deploy Project Artifacts to Vercel
          command: vercel deploy --prebuilt --prod --token=$VERCEL_TOKEN

workflows:
  version: 2
  preview_and_production:
    jobs:
      - preview_deployment:
          filters:
            branches:
              ignore: /main/
      - production_deployment:
          filters:
            branches:
              only: /main/

The preview_deployment job will run when your code is pushed to a git branch other than main, and the production_deployment job will run when code is merged into the main branch.

Next, add the required values from Vercel as environment variables in CircleCI:

1. Retrieve your Vercel Access Token
2. Install the Vercel CLI and run vercel login
3. Inside your folder, run vercel linkto create a new Vercel project
4. Inside the generated .vercelfolder, save the projectId and orgId from the  project.json
5. In CircleCI, add VERCEL_TOKEN, VERCEL_ORG_ID, and VERCEL_PROJECT_ID as Environment Variables

Now that your Vercel application is configured with CircleCI, you can try out the workflow:

• Create a new pull request to your repository
• CircleCI will recognize the change and use the Vercel CLI to build your application
• The job uploads the build output to Vercel and creates a Preview Deployment
• When the pull request is merged, a Production build is created and deployed

Every pull request will now automatically have a Preview Deployment attached. If the pull request needs to be rolled back, you can revert and merge the PR and Vercel will start a new Production build back to the old git state.