Web previews for pull requests

Web previews offer development and quality assurance (QA) teams a way to preview changes from pull requests (PRs) before merging code to a production or integration branch. Pull requests let you tell others about changes you’ve pushed to a branch in a repository. After a pull request is opened, you can discuss and review the potential changes with collaborators and add follow-up commits before your changes are merged into the base branch.

A web preview deploys every pull request made to your repository to a unique preview URL which is completely different from the URL your main site uses. For apps with backend environments provisioned using the Amplify CLI or Amplify Studio, every pull request (private Git repositories only) creates a temporary backend that is deleted when the PR is closed.

When web previews are turned on for your app, each PR counts toward the Amplify quota of 50 branches per app. To avoid exceeding this quota, make sure to close your PRs. For more information about quotas, see Amplify Hosting service quotas.

Note

Currently, the AWS_PULL_REQUEST_ID environment variable is not available when using AWS CodeCommit as your repository provider.

Enable web previews

For apps stored in a GitHub repo, previews use the Amplify GitHub App for repo access. If you are enabling web previews on an existing Amplify app that you previously deployed from a GitHub repo using OAuth for access, you must first migrate the app to use the Amplify GitHub App. For migration instructions, see Migrating an existing OAuth app to the Amplify GitHub App.

Important

For security purposes, you can enable web previews on all apps with private repositories, but not on all apps with public repositiories. If your Git repository is public, you can set up previews only for apps that don't require an IAM service role.

For example, apps with backends and apps that are deployed to the WEB_COMPUTE hosting platform require an IAM service role. Therefore, you can't enable web previews for these types of apps if their repository is public.

Amplify enforces this restriction to prevent third parties from submitting arbitrary code that would run using your app's IAM role permissions.

To enable web previews for pull requests

1. Choose Hosting, then Previews.

   Note

   Previews is visible in the App settings menu only when an app is set up for continuous deployment and connected to a git repository. For instructions on this type of deployment, see Getting started with existing code.

2. For GitHub repositories only, do the following to install and authorize the Amplify GitHub App in your account:

   1. In the Install GitHub App to enable previews window, choose Install GitHub app.

   2. Select the GitHub account where you want to configure the Amplify GitHub App.

   3. A page opens on Github.com to configure repository permissions for your account.

   4. Do one of the following:

      • To apply the installation to all repositories, choose All repositories.

      • To limit the installation to the specific repositories that you select, choose Only select repositories. Make sure to include the repo for the app that you are enabling web previews for in the repositories that you select.

   5. Choose Save

3. After you enable previews for your repo, return to the Amplify console to enable previews for specific branches. On the Previews page, select a branch from the list and choose Edit settings.

4. On the Manage preview settings page, turn on Pull request previews. Then choose Confirm.

5. For fullstack applications do one of the following:

   • Choose, Create new backend environment for every Pull Request. This option enables you to test changes without impacting production.

   • Choose Point all Pull Requests for this branch to an existing environment.

6. Choose Confirm.

The next time you submit a pull request for the branch, Amplify builds and deploys your PR to a preview URL. After the pull request is closed, the preview URL is deleted, and any temporary backend environment linked to the pull request is deleted. For GitHub repositories only, you can access a preview of your URL directly from the pull request in your GitHub account.

Web preview access with subdomains

Web previews for pull requests are accessible with subdomains for an Amplify app that is connected to a custom domain managed by Amazon Route 53. When the pull request is closed, branches and subdomains associated with the pull request are automatically deleted. This is the default behavior for web previews after you set up pattern-based feature branch deployments for your app. For instructions on setting up automatic subdomains, see Set up automatic subdomains for an Amazon Route 53 custom domain.