
When you [connect your application to GitHub](/docs/how-to/github), Encore will begin to automatically provision ephemeral Preview Environments for each Pull Request. Preview Environments are fully functional, isolated, environments where you can test your application as it would run in production.

Preview Environments are named after the pull request, for example PR #72 creates a Preview Environment named `pr:72` with the API base url `https://pr72-$APP_ID.encr.app`.

You can also view the environment in the Cloud Dashboard, where the url will be `https://app.encore.dev/$APP_ID/envs/pr:72`.

## Preview Infrastructure

Preview Environments run in Encore's free development cloud, removing the need to manually manage and pay for your own sandbox environments. This gives you a cost-efficient way to validate your changes before they are merged and deployed to the [primary environment](/docs/deploy/environments#primary-environment).

See the [infra docs](/docs/deploy/infra#preview-environments) if you're curious about exactly how Preview Environments are provisioned.

![Preview environment linked in GitHub](/assets/docs/ghpreviewenv.png "Preview environment linked in GitHub")

## Frontend Collaboration

Preview Environments make it really easy to collaborate and test changes with your frontend. Just update your frontend API client to point to the `pr:#` environment.
This is a one-line change since your API client always specifies the environment name, e.g. `https://<env>-<my-app>.encr.app/`.

If your pull request makes changes to the API, you can [generate a new API client](/docs/develop/client-generation)
for the new backend API using `encore gen client --env=pr:72 --lang=typescript my-app`
