Page Builder Sandwich: Developers

What it does

• Register your own blocks and controls — Documented PHP and JavaScript APIs to add blocks, style controls, dynamic data sources, display conditions and form actions.
• Hooks and filters everywhere — Documented actions and filters for rendering, saving, assets and the editor, following modern WordPress conventions.
• REST API and WP-CLI — Manage templates, regenerate CSS and run imports from the command line or other apps.
• Developer docs and starter kit — A public docs site, TypeScript types and an example add-on plugin to copy.
• Old developer API still supported — Third-party add-ons written for the old pbsAddInspector/pbs_shortcodes API keep working through a compatibility layer.

Free or Pro

Everything here is in the free edition.