Upgrading is the process of moving your site from a previous major version of Drupal to a newer version, for example from Drupal 7 to Drupal 8. This consists of upgrading the codebase to the appropriate version and then migrating the data from your old site into the new one. Drupal 8 core contains two modules to help facilitate this process: Migrate Drupal and Migrate Drupal UI.
Make sure you understand the difference between updating and upgrading. If you already have a Drupal 8 site and want to move to another minor version, see the Minor Version and Security Updates topic.
- Upgrade a site from Drupal 6 to Drupal 8
- Upgrade a site from Drupal 7 to Drupal 8
The upgrade process, and underlying Migration API, are still evolving. We don't anticipate them changing dramatically even though they are still marked experimental. Beware of any resources that were written before Drupal 8.1.x was released (April 19, 2016) as the system changed considerably in ways that invalidate many of the older articles.