App Engine Standard Environment Runtimes

The App Engine standard environment has two generations of runtime environments. The second generation runtimes significantly improve the capabilities of App Engine and remove some of the limitations of the first generation runtimes. This page describes the similarities and differences between the first and second generation runtimes.

First generation Second generation
Supported languages Python 2.7
PHP 5.5
Go 1.9
Python 3.7
Java 8
PHP 7.2 (beta)
Go 1.11 (beta)
Language extension and system library support Whitelisted extensions and libraries only Any extension or library
External network access Via URL Fetch API Full access
File system access None Read and write access to /tmp
Language runtime Modified for App Engine Unmodified, open source runtime
Isolation mechanism Proprietary gVisor-based container sandbox

App Engine first generation runtime support

There are no plans to deprecate the App Engine first generation runtimes at this time. The second generation runtimes represent the future direction of App Engine; however, developers and customers using the first generation runtimes will continue to receive support and feature updates.

Similarities between first and second generation runtimes

  • Nearly instantaneous scale-up time to respond to traffic spikes.
  • Applications are built using the same build process.
  • Same SLA for GA services.
  • Identical gcloud command support and the same GCP console interface.
  • Free tier.
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App Engine Documentation