Gutenberg 9.9: New JSON structure for theme.json files

Gutenberg 9.9 changes the structure of theme.json files for experimental Full Site Editing (FSE) themes.

The changes made are a first step to allowing theme metadata and more granular control for FSE in the future. More details on that process and what to expect in the future can be found in the Overview GitHub ticket.

The Documentation for theme.json has been updated and is properly maintained so theme developers experimenting with FSE can follow that and update their files accordingly.

The structural changes that went in Gutenberg 9.9 can be found in Pull Request #28110 in the Gutenberg project and can be summed-up in the following:

• settings and styles and now on the root level of the JSON file
• global was renamed to root

With settings and styles in the root level it is now easier to group all block settings in one place and all block styles in a separate area, therefore making it easier to navigate the file and get an overview, while at the same time making it easier to extend the file’s functionality in the future.

Before:

{
  "global": {
    "settings": { ... },
    "styles": { ... }
  },
  "core/paragraph": {
    "settings": { ... },
    "styles": { ... }
  }
}

After:

{
  "settings": {
    "defaults": { ... },
    "root": { ... },
    "core/paragraph": { ... }
  },
  "styles": {
    "root": { ... },
    "core/paragraph": { ... }
  }
}