Steps to upgrade, perform a guided migration, or migrate manually to Drupal 9 on Pantheon.

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Drupal 9 includes many of the features and layout that Drupal 8 users are familiar with, and it removes deprecated code to help improve future Drupal development.

Drupal 9 updates Drupal’s underlying dependencies like Symfony 4.4 and Twig 2, removes several deprecated API functions in favor of better options, and allows everyone running Drupal 8.8+ an easy upgrade path to Drupal 9 and beyond.

There are a number of ways to upgrade to Drupal 9 on Pantheon, and we're building out the documentation within this guide to try to help you through your adventure.

See our Drupal 9 and Integrated Composer docs to learn more about Drupal 9 on Pantheon, and to get started with a fresh new site.