WordPress v.5 update breaks the Classic Editor

As you might know, the WordPress team published a major version 5 update on December 6th, 2018.
The update provides improved stability and performance, introducing new native Gutenberg visual block-editor that is there for long.

The ‘Classic Editor’ plugin was introduced by the WordPress team in order to temporarily disable the inbuilt Gutenberg functionality and replace it with a familiar editing interface. This downgrade was promised to be supported till 2021 and will allow you to use the existing Themes with Custom Post fields since then.

Please be aware, that your website’s back-end editor might go completely blank after an update. This has happened to several of my client’s websites and I recommend implementing this major update on cloned staging environment first.

In order to restore the editing functionality after an update, please try the following:

1. Create a full Backup of your website
2. Update WordPress Core to v.5.
3. Install ‘Classic Editor’ plugin, activate.
4. Adjust the WordPress Writing settings in Admin > Settings > Writing to:
   – The default editor for all users: Classic Editor
   – Allow users to switch editors: No

The above adjustments should do the trick and will enable you to use the familiar Classic Editor.