Test and deploy your application

Region ID

The REGION_ID is an abbreviated code that Google assigns based on the region you select when you create your app. The code does not correspond to a country or province, even though some region IDs may appear similar to commonly used country and province codes. For apps created after February 2020, REGION_ID.r is included in App Engine URLs. For existing apps created before this date, the region ID is optional in the URL.

Learn more about region IDs.

Learn how to run your application locally, deploy it, and test on App Engine.

Run locally

To test your application before deploying, run your application in your local environment with the development tools that you usually use.

Before deploying your application

Before deploying your application:

Deploy your application

Deploy your application to App Engine using the gcloud app deploy command. During deployment, the Cloud Build service builds a container image of your application to run in the standard environment. Each build is run in the same region as your Google Cloud project. For more information, see Manage build images.

To programmatically deploy your apps, use the Admin API.

Deploy a service

You deploy your application to App Engine by deploying versions of your application's services and each of their configuration files.

To deploy a version of your application's service, run the following command from the directory where the app.yaml file of your service is located:

gcloud app deploy

Specifying no files with the command deploys only the app.yaml file in your current directory. By default, the deploy command generates a unique ID for the version that you deploy, deploys the version to the Google Cloud project you configured the Google Cloud CLI to use, and routes all traffic to the new version.

You can change the default behavior of the command by targeting specific files or including additional parameters:

  • To deploy the other configuration files of your service, you must target and deploy each file separately. For example:
    gcloud app deploy cron.yaml
    gcloud app deploy dispatch.yaml
    gcloud app deploy index.yaml
  • To specify a custom version ID, use the --version flag.
  • To prevent traffic from being automatically routed to the new version, use the --no-promote flag.
  • To deploy to a specific Google Cloud project, use the --project flag.

For example, to deploy the service defined by the app.yaml file to a specific Google Cloud project, assign it a custom version ID, and prevent traffic from being routed to the new version:

gcloud app deploy --project PROJECT_ID --version VERSION_ID --no-promote

For more information about this command, see the gcloud app deploy reference.

Deploy multiple services

You use the same deployment command for deploying or updating the multiple services that make up your application.

Before you begin:

  • You must initially deploy a version of your application to the default service before you can create and deploy subsequent services.
  • The ID of each of your services must be specified in their corresponding app.yaml configuration files. To specify the service ID, include the service element definition in each configuration file. By default, excluding this element definition from your configuration file deploys the version to the default service.

To deploy multiple services, separately deploy each service's app.yaml file. You can specify multiple files with a single gcloud app deploy command:

gcloud app deploy service1/app.yaml service2/app.yaml

View build logs

Cloud Build streams build and deploy logs that are viewable in the Cloud Build Build history section of the Google Cloud console. To view builds in the app's region, use the Region menu to filter by the region.

Manage build images

Each time you deploy a new version:

  1. App Engine creates a container image using the Cloud Build service.

  2. Cloud Build builds the container image in the app's region, and runs in the App Engine standard environment.

  3. App Engine stores built container images in Artifact Registry. You can download these images to keep or run elsewhere.

After deployment is complete, App Engine no longer needs the container images. The container images aren't automatically deleted. To avoid reaching your storage quota, you can safely delete any images you don't need. However, if you might need the images in the future or want to keep a copy of the images, you need to export a copy prior to deletion. For more information about managing images in Artifact Registry, see Manage images.

Ignore files

You can use a .gcloudignore file to specify files and directories that won't be uploaded to App Engine when you deploy your services. This is useful for ignoring build artifacts and other files that don't need to be uploaded with your deployment.

View your application

After you deploy your application to App Engine, you can run the following command to launch your browser and view it at https://PROJECT_ID.REGION_ID.r.appspot.com:

gcloud app browse

Test on App Engine before shifting traffic

Before configuring a new version to receive traffic, you can test it on App Engine. For example, to test a new version of your default service:

  1. Deploy your new version, but prevent traffic from being automatically routed to the new version:

    gcloud app deploy --no-promote

  2. Access your new version by navigating to the following URL:


    Now you can test your new version in the App Engine runtime environment. You can debug your application by viewing its logs. For more information, see Writing Application Logs.

    App Engine routes requests sent to https://PROJECT_ID.REGION_ID.r.appspot.com to the version previously configured to receive traffic.

  3. When you want to send traffic to the new version, use the Google Cloud console to migrate traffic:

    Manage versions

    Select the version you just deployed and click Migrate traffic.

You can use the same process to test new versions of other services by replacing default in the URL with your service's name:


For more information about targeting specific services and versions, see How requests are routed.

Use build environment variables

You can set build environment variables for runtimes that support buildpacks.

Build environment variables are key-value pairs that you can specify to configure the buildpack you use to deploy your app. For example, you might want to specify compiler options.

Before you begin:

  • Keys must start with an uppercase ASCII letter, and can include uppercase ASCII letters, digits, and underscores.
  • You should avoid creating any variables with a GOOGLE_* key prefix.
  • The following keys are reserved for Google's use:
  • You can use any key that is supported by buildpacks.

To use environment variables with buildpacks, specify the build_env_variables field in your app.yaml file.

Learn more about buildpacks.

Use Cloud Trace

Cloud Trace is useful for understanding how requests propagate through your application. You can inspect detailed latency information for a single request or view aggregate latency for your entire application.

To view trace details in Cloud Trace, you can follow Find and explore traces. In the Trace explorer, you can use the filters to filter by your specific App Engine service and version.