A theme’s theme.json file is one of the best ways to curate the Editor experience and will likely be the first tool you use before reaching for more sophisticated solutions.

Providing default controls/options

Since theme.json acts as a configuration tool, there are numerous ways to define at a granular level what options are available. This section will use duotone as an example since it showcases a feature that cuts across a few blocks and allows for varying levels of access.

Duotone with Core options and customization available for each image related block:

{
    "version": 3,
    "settings": {
        "color": {
            "customDuotone": true,
            "duotone": [
            ]
        }
    }
}

Duotone with theme defined color options, Core options, and customization available for each image related block:

{
    "version": 3,
    "settings": {
        "color": {
            "duotone": [
                {
                    "colors": [ "#000000", "#ffffff" ],
                    "slug": "foreground-and-background",
                    "name": "Foreground and background"
                },
                {
                    "colors": [ "#000000", "#ff0200" ],
                    "slug": "foreground-and-secondary",
                    "name": "Foreground and secondary"
                },
                {
                    "colors": [ "#000000", "#7f5dee" ],
                    "slug": "foreground-and-tertiary",
                    "name": "Foreground and tertiary"
                },
            ]
        }
    }
}

Duotone with defined default options and all customization available for the Post Featured Image block:

{
    "version": 3,
    "settings": {
        "color": {
            "custom": true,
            "customDuotone": true
        },
        "blocks": {
            "core/post-featured-image": {
                "color": {
                    "duotone": [
                        {
                            "colors": [ "#282828", "#ff5837" ],
                            "slug": "black-and-orange",
                            "name": "Black and Orange"
                        },
                        {
                            "colors": [ "#282828", "#0288d1" ],
                            "slug": "black-and-blue", 
                            "name": "Black and Blue"
                        }
                    ],
                    "customDuotone": true,
                    "custom": true
                }
            }
        }
    }
}

Duotone with only defined default options and core options available for the Post Featured Image block (no customization):

{
    "version": 3,
    "settings": {
        "color": {
            "custom": true,
            "customDuotone": true
        },  
        "blocks": {
            "core/post-featured-image": {
                "color": {
                    "duotone": [
                        {
                            "colors": [ "#282828", "#ff5837" ],
                            "slug": "black-and-orange",
                            "name": "Black and Orange"
                        },
                        {
                            "colors": [ "#282828", "#0288d1" ],
                            "slug": "black-and-blue",
                            "name": "Black and Blue"
                        }
                    ],
                    "customDuotone": false,
                    "custom": false
                }
            }
        } 
    }
}

Limiting interface options with theme.json

Limit options on a per-block basis

Beyond defining default values, using theme.json allows you to also remove options entirely and instead rely on what the theme has set in place. Below is a visual showing two extremes with the same paragraph block:

Continuing the examples with duotone, this means you could allow full access to all Duotone functionality for Image blocks and only limit the Post Featured Image block like so:

{
    "version": 3,
    "settings": {
        "color": {
            "custom": true,
            "customDuotone": true
        },
        "blocks": {
            "core/image": {
                "color": {
                    "duotone": [],
                    "customDuotone": true,
                    "custom": true
                }
            },
            "core/post-featured-image": {
                "color": {
                    "duotone": [],
                    "customDuotone": false,
                    "custom": false
                }
            }
        }
    }
}

You can read more about how best to turn on/off options with theme.json here.

Disable inherit default layout

To disable the “Inherit default layout” setting for container blocks like the Group block, remove the following section:

"layout": {
    "contentSize": null,
    "wideSize": null
},

Limit options globally

When using theme.json in a block or classic theme, these settings will stop the default color and typography controls from being enabled globally, greatly limiting what’s possible:

{
    "version": 3,
    "settings": {
        "layout": {
            "contentSize": "750px"
        },
        "color": {
            "background": false,
            "custom": false,
            "customDuotone": false,
            "customGradient": false,
            "defaultGradients": false,
            "defaultPalette": false,
            "text": false
        },
        "typography": {
            "customFontSize": false,
            "dropCap": false,
            "fontStyle": false,
            "fontWeight": false,
            "letterSpacing": false,
            "lineHeight": false,
            "textDecoration": false,
            "textTransform": false
        }
    }
}

To enable something from the above, just set whatever value you want to change to true for more granularity.