Key Takeaways
- WordPress 5.8 delivered the Site Editor in beta — functional for development and experimentation with block themes, but not yet fully stable for all production use cases.
- Block-based widget areas arrived in 5.8, replacing the classic Widgets screen — sites running theme widget areas now configure them through the block editor instead of the widget drag-and-drop interface.
- The Query Loop block enables dynamic post display without PHP code — a significant capability for theme developers building archive templates, portfolio grids, and custom post type displays.
- Theme.json is the global style configuration file for block themes — defining available colours, typography, spacing, and default block styles centrally rather than in per-block CSS.
- Full Site Editing's full capability — stable, documented, with broad ecosystem theme support — arrived progressively through WordPress 5.9 (Twenty Twenty-Two, stable Site Editor) and 6.0 (design tools expansion).
The WordPress development community set an ambitious goal for 2021: ship the first phase of Full Site Editing to WordPress core. WordPress 5.8 — released July 20, 2021 and named 'Tatum' after the jazz pianist Art Tatum — delivered that milestone. What arrived in 5.8 was consequential but intentionally incomplete. The Gutenberg team has publicly described FSE development as a multi-year, multi-phase project. The 5.8 release delivered the infrastructure and core blocks needed to begin FSE, with the understanding that stability, documentation, and ecosystem support would continue to mature through subsequent releases. For WordPress users and developers, understanding what 5.8 actually delivered — versus what's still in development — helps set appropriate expectations for block theme adoption and site development decisions.
Definition: Theme.json in WordPress Block Themes
Theme.json is a JSON configuration file that block themes use to define design system settings — the palette of available colours, the typography options (font families, font sizes, font weights), and the spacing scale available to blocks through the editor settings panel. It replaces the need to add_theme_support() functions in functions.php for configuring editor colour palettes and font sizes. Theme.json can also set default styles for specific blocks (e.g., the default heading font size for h2 blocks), enable or disable block features (e.g., disable colour customisation for text blocks), and define global CSS custom properties used throughout the theme. The result: a single file defines the design constraints and defaults of the entire block theme, ensuring that block styling choices in the editor align with the overall design system.
What WordPress 5.8 Actually Delivered for Full Site Editing
WordPress 5.8 shipped the foundational FSE components — the Site Editor, Query Loop block, and theme.json — while intentionally marking the Site Editor as experimental to set expectations for its maturation trajectory.
The Site Editor in 5.8 is accessible at Appearance > Editor when a block theme is active. Within the Site Editor, you can navigate between templates (the page-type templates: singular, archive, 404, search) and template parts (header, footer, sidebar — the reusable sections used across templates), and edit them using the block editor interface. Global Styles (the paintbrush icon in the Site Editor toolbar) provides access to site-wide colour, typography, and spacing settings defined by theme.json. In 5.8, the Site Editor was marked as beta — some workflows were incomplete, certain blocks behaved differently in the template editing context, and some themes had inconsistencies. Developers could build with it; production deployment required careful testing.
Block-based widget areas in 5.8 replaced the classic Appearance > Widgets screen with the block editor interface. Sidebar, footer, and other registered widget areas now display as block editor canvases where you add, arrange, and configure blocks rather than dragging classic widgets. The change breaks backwards compatibility with classic widgets — sites running custom or third-party classic widgets (not converted to blocks) needed the Classic Widget plugin to restore the old interface. Most major widget authors had block equivalents by the 5.8 release, but the transition required verification for each site.
The Query Loop block is arguably 5.8's most useful contribution for theme developers. Before this block, displaying dynamic post lists in a customisable layout required PHP loop code in template files. The Query Loop block replaces this with a visual configuration: select the post type (Posts, Pages, or registered custom post types), filter by category/tag/author, set the number of posts, define the order, and configure the layout using inner blocks. The Post Template block within Query Loop defines the repeating layout for each result — using blocks like Post Featured Image, Post Title, Post Date, and Post Excerpt to build the display format.
- Site Editor (beta) — edit templates and template parts through block interface; requires block theme
- Block-based widget areas — Widgets screen replaced with block editor; classic widget support via plugin
- Query Loop block — dynamic post display without PHP; configurable post type, filters, layout
- Theme.json — JSON design system configuration file defining colours, typography, spacing for block themes
- Template Editor — edit post/page templates from within the post editor without going to the Site Editor
The FSE Roadmap Beyond 5.8
Full Site Editing matured through WordPress 5.9 and 6.0, with the Site Editor stabilising and the block theme ecosystem expanding — the 5.8 beta became production-ready infrastructure within two release cycles.
WordPress 5.9 (January 2022) was the release that brought FSE to production readiness. It shipped Twenty Twenty-Two — the first default WordPress theme built entirely as a block theme, using HTML templates and theme.json rather than PHP templates. The Site Editor received significant stability improvements, a restructured navigation UI, and expanded Global Styles capabilities. Twenty Twenty-Two demonstrated the full FSE experience as a production theme rather than a developer experiment — and its open-source code became the reference implementation for block theme development.
WordPress 6.0 (May 2022) continued the FSE maturation with a focus on design tools — expanded spacing controls, border design tools for blocks, block locking (preventing specific blocks from being moved or deleted in templates), and improvements to the global styles interface. By 6.0, FSE was sufficiently stable for production use on new builds and theme rebuilds — though the ecosystem of third-party block themes and block plugins continued to evolve throughout 2022 and into 2023.
Experience Signal
The WordPress 5.8 FSE launch coincided with several client projects where we were evaluating whether to build on classic themes vs block themes. Our decision was to continue using proven classic themes with Gutenberg for content editing for client projects through late 2021, while building internal block theme projects to develop FSE expertise. By early 2022 (post-5.9), we shifted to recommending block themes for new builds — the Site Editor was stable, Twenty Twenty-Two demonstrated the full experience, and the block ecosystem had matured enough for production use. That timing — not rushing to FSE in 5.8, but not waiting indefinitely — was the right call for balancing feature benefit with stability risk.
Frequently Asked Questions
The WordPress Site Editor (also called the FSE editor or the Global Site Editor) is the interface that allows editing all aspects of a block-based WordPress theme — headers, footers, templates, template parts, and global styles — using the same block editing interface as the post/page editor. In WordPress 5.8, the Site Editor launched in beta, accessible through Appearance > Editor when a block theme (like Twenty Twenty-One with FSE support enabled, or the Gutenberg plugin's default themes) is active. The Site Editor shows the entire site template, not just post content — editors can select and modify the header, modify the sidebar, change the footer, and switch between page templates, all through the block interface. In 5.8, the Site Editor was experimental — full stability and documentation arrived progressively through 5.9 and 6.0.
The Query Loop block (introduced in WordPress 5.8) is a block that displays a dynamic list of posts based on query parameters — essentially a visual, block-based way to create the functionality that previously required PHP loop code. You configure the Query Loop block to show a specific post type, filtered by category, tag, or custom taxonomy, with a defined layout (number of posts, order, included/excluded post IDs). Inner blocks within the Query Loop (Post Title, Post Featured Image, Post Date, Post Excerpt) define how each post in the loop is displayed. The Post Template block (inside Query Loop) defines the layout of each result. This makes it possible to create custom blog archives, portfolio grids, testimonial feeds, and custom post type archives without PHP code — through the block editor.
Yes. Full Site Editing — specifically the Site Editor and the ability to edit templates, template parts, and global styles — requires an active block theme. Block themes use HTML template files (with block markup) instead of PHP template files, and declare FSE support in their theme.json configuration. WordPress 5.8 introduced Twenty Twenty-One with FSE support via the Gutenberg plugin, and Twenty Twenty-Two became the first default block theme in WordPress 5.9. Classic themes (themes using PHP templates) do not support the Site Editor — the Appearance > Editor menu item only appears when a block theme is active. Classic themes continue to work normally; they just don't benefit from FSE features.
Sources
Building a New WordPress Site or Migrating to Block Themes?
Webnixon designs and builds block-theme WordPress sites using Full Site Editing — from theme.json design systems through template development and content team training.
Book a WordPress ConsultationAbout the author
David Okafor
Developer
David is a full-stack developer at Webnixon with expertise in React, WordPress, and custom web application development. He contributes to complex front-end builds, API integrations, and performance-focused engineering for Webnixon clients. He writes about web development best practices, WordPress, and the technical side of building fast, maintainable websites.
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