JuZ Rich Text Extender

JuZ Rich Text Extender allows developers to register custom inline format buttons in the Gutenberg (block editor) toolbar. Each button applies a specific HTML inline tag with an optional CSS class to the selected text.

The plugin includes a built-in nesting validation system: buttons are automatically disabled when their use would produce invalid HTML nesting (e.g. <a> inside <a>). When a format is already active, its button remains enabled so it can always be toggled off.

Key features:

• Register custom inline formats (tag + CSS class) via a WordPress filter
• tagName defaults to span, which is strongly recommended for compatibility
• Smart nesting validation against the full active tag stack (for non-span tags)
• Buttons are visually disabled when nesting is not allowed
• Exhaustive inline tag ruleset (span, a, strong, em, mark, code, u, s, i, b, q, cite, abbr, small, sub, sup)
• Inline tag rules are filterable for full customisation by themes or other plugins

Live demo:
See it in action on playground.juzed.dev, or try it in the editor with WordPress Playground, nothing to install.

For developers:

Formats and inline tag rules are both exposed via WordPress filters, making the plugin fully extensible without modifying core files.