WordPress 5.9 represents the largest release of Gutenberg features since the initial Gutenberg launch in WordPress 5.0. In addition, WordPress 5.9 includes 99 enhancements including Full Site Editing and 100 bug fixes.
Important things to know:
- You need a block-based theme to actually use Full Site Editing. A block theme is a WordPress theme with templates entirely composed of blocks so that in addition to the post content of the different post types (pages, posts, …), the block editor can also be used to edit all areas of the site: headers, footers, sidebars, etc. Chances are: you aren’t using a block-based theme at the moment.
- Full Site Editing is still in a current phase as a minimum viable product. This allows for a gradual adoption from users as most themes are still not ready to utilize this functionality or would be incompatible moving forward.
- You don’t have to adopt Full Site Editing. If you aren’t ready for a block-based theme just yet, don’t worry. “Classic” themes continue to exist and work as always.
See the official details at https://wordpress.org/news/2022/01/josephine/.