Your Drupal 8 to Drupal 9 upgrade will be "insanely" smooth. So they say... With Drupal 9 built in Drupal 8, all there's left for you to do is to remove all deprecated API from your website. Easier said than done. Just imagine yourself fine-tooth combing your codebase to: identify all errors and fix them, one by one, identify all deprecated code and remove it, manually, one by one, apply the same code updates, repetitively, as many times as needed. But what if you could automate deprecated API use removal from your Drupal site? You can, actually, with Rector-Drupal....