Full Site Editing (FSE) and block themes: what changed in WordPress
TL;DR: Full Site Editing (FSE) extended the block editor's reach from just post and page content to your site's entire structure, headers, footers, templates, and global styles, all editable through the same visual block interface rather than requiring PHP theme file edits or a separate theme customizer. A "block theme" is specifically built to support this, using HTML template files with block markup rather than traditional PHP template files, a genuinely structural shift in how much site-wide design control is directly available to a non-developer through WordPress's native admin interface, distinct from and complementary to the page-builder-versus-Gutenberg comparison covered in our dedicated guide.
What editing looked like before FSE
Prior to Full Site Editing, the block editor (Gutenberg) governed only the content area within a post or page, the actual body content a visitor reads, while the surrounding structural elements, your site's header, footer, sidebar layout, and overall template structure, remained defined in the theme's own PHP template files, editable only by someone comfortable directly modifying theme code, or through a more limited theme customizer interface offering some visual configuration options but nowhere near the granular, block-level control available for actual content.
What FSE actually changed
FSE extends the same block-based editing paradigm used for post and page content to these previously code-locked structural elements, meaning a site owner using a properly built block theme can now edit their header, footer, and overall page templates directly through the same visual, block-based Site Editor interface, without touching PHP code at all, a genuinely structural expansion of what "editing a WordPress site" means, moving considerably more design control into the native, no-code WordPress admin experience than was previously available outside of a dedicated page builder plugin.
Block themes vs classic themes
A "block theme" (also called an FSE theme) is specifically built using HTML template files containing block markup, rather than the traditional PHP template files (header.php, footer.php, and similar) that classic WordPress themes use, and this underlying structural difference is what actually enables full site editing capability for that specific theme. A "classic theme," built the traditional way with PHP templates, does not support full site editing regardless of how current or well-maintained it otherwise is, since the underlying template architecture is fundamentally different; classic themes continue to function normally and remain fully supported, but they retain the older, more limited editing model rather than gaining FSE capability simply through a WordPress core update.
Global styles: a specific new capability
Block themes support a "Global Styles" system, allowing site-wide typography, color palette, and spacing settings to be defined and adjusted centrally through the Site Editor interface, with these settings automatically applying consistently across the entire site rather than needing to be configured separately within each individual page or template, a genuine convenience and consistency improvement for a site owner wanting to make a site-wide design adjustment (a color palette change, for example) without needing to manually update many separate pages or templates individually.
Template parts and reusability
FSE introduces "template parts," reusable structural components (a header, a footer, a specific sidebar configuration) that can be defined once and reused consistently across multiple templates, with an edit to a shared template part automatically reflected everywhere it is used, a genuinely useful capability for maintaining consistency across a site with multiple distinct page templates (a different layout for blog posts versus a landing page, for example) that nonetheless share common structural elements like a consistent header and footer.
A comparison table
| Factor | Classic theme | Block theme (FSE) |
|---|---|---|
| Template structure | PHP files | HTML files with block markup |
| Header/footer editing | Requires theme code editing or a separate customizer | Directly editable via the Site Editor |
| Global style management | Varies, often more limited or theme-specific | Centralized Global Styles system |
| Template reusability | Theme-code-dependent | Native template parts |
| Non-technical site-wide design control | More limited | Considerably expanded |
Is FSE the same as Elementor or other page builders?
Related in the general sense of both providing visual, no-code design control, but genuinely distinct in scope and underlying approach: FSE is native to WordPress core itself, requiring no additional plugin, and specifically extends the standard block editor's paradigm to the entire site, while page builders like Elementor (covered in our dedicated comparison) are third-party plugins with their own distinct editing interface and underlying architecture, generally offering more elaborate design flexibility at the cost of the added plugin dependency and generally heavier page weight discussed in that comparison. A site owner choosing between a block theme with FSE and a traditional theme plus a page builder is making a genuinely similar kind of trade-off (native, lighter-weight simplicity versus third-party, more elaborate flexibility) to the one covered in our dedicated Elementor-vs-Gutenberg comparison, just extended to the entire site structure rather than individual page content alone.
FAQs
Can I switch from a classic theme to a block theme without losing my content?
Yes, your actual post and page content, stored in WordPress's database independently of the theme, remains intact through a theme switch; what changes is how your site's structural elements (header, footer, template layout) are defined and edited, which may require rebuilding or reconfiguring those structural elements to match your new block theme's approach.
Do I need to know how to code to use Full Site Editing?
No, this is specifically the point of FSE, extending visual, block-based editing to structural elements that previously required code changes, meaning a non-technical site owner can now adjust their header, footer, and overall template design directly through the Site Editor's visual interface without touching PHP.
Are all current WordPress themes block themes now?
No, both classic and block themes continue to be actively developed and used; many established, popular themes remain classic themes, either because they have not yet been rebuilt using the newer block theme architecture, or because their developers have deliberately chosen to continue supporting the classic theme model for compatibility or other specific reasons.
Does using a block theme mean I can't use any plugins that add their own blocks or functionality?
No, block themes remain fully compatible with the broader WordPress plugin ecosystem generally, including plugins that add their own custom blocks; the block theme architecture specifically affects how the theme's own template structure is built, not your ability to use standard, well-built plugins alongside it.
Is FSE mature and stable enough to use for a genuine business site today?
FSE has matured considerably since its initial introduction and is now a well-established, actively used part of core WordPress, though the specific maturity and polish of any individual block theme still varies by that theme's own quality and how thoroughly it has been built to take advantage of FSE's capabilities, worth evaluating a specific theme's actual quality and reviews rather than assuming uniform maturity across every available block theme option.
Does FSE affect site performance compared to a classic theme?
Generally, a well-built block theme can be genuinely lightweight, similar in spirit to the lightweight theme comparison covered in our dedicated guide, though actual performance still depends on the specific theme's implementation quality and how much additional plugin functionality is layered on top, rather than FSE inherently guaranteeing better or worse performance purely by virtue of using the newer architecture.
Can I still use the WordPress Customizer with a block theme?
The traditional Customizer interface is largely superseded by the Site Editor for block themes, since block themes handle the equivalent design and layout configuration through the newer, more comprehensive Site Editor interface instead, meaning the workflow shifts to this newer tool rather than the older Customizer for sites using a genuine block theme.
Conclusion
Full Site Editing represents a genuinely structural expansion of what WordPress's native, no-code editing capability covers, extending block-based visual editing from just post and page content to a site's entire structure, headers, footers, templates, and global styles, specifically enabled by block themes' HTML-and-block-markup architecture rather than the traditional PHP templates classic themes use.
This gives a non-technical site owner considerably more direct, native design control than was previously available outside of a dedicated third-party page builder, while classic themes and traditional theme development remain fully valid, actively supported approaches for sites and developers not yet ready or needing to move to the newer block theme architecture.
HostCloud's hosting supports both classic and block themes without any specific configuration limitations, and our team can advise on which approach genuinely fits your specific site's design and maintenance needs. See plans at https://hostcloud.in.