When WordPress introduced Full Site Editing (FSE) with WordPress 5.9 in early 2022, most developers dismissed it as a beta experiment. Three years on, FSE is powering some of the web's most performant sites — and if you're planning a new website in 2025, you need to understand what it means for your project.
What is WordPress Full Site Editing?
FSE replaces the traditional WordPress editor with a unified block-based system that controls your entire site — headers, footers, templates, and page content — using the same visual interface. Before FSE, you'd edit page content in the block editor but rely on your theme's PHP templates for headers and footers. FSE collapses that distinction.
The key concept is the block theme: a WordPress theme that's built entirely from blocks rather than PHP template files. Block themes use a theme.json file to define global styles — fonts, colours, spacing — and a templates folder of block-based HTML for page layouts.
What's Actually Changed in 2025
The 2024–2025 Gutenberg development cycle focused on two areas that make FSE genuinely viable for client sites:
1. Interactivity API
WordPress 6.5 shipped the Interactivity API — a lightweight, PHP-rendered approach to adding real-time UI behaviour (accordions, tabs, live filters) without loading a full JavaScript framework. For performance-obsessed developers, this is significant: you get dynamic UI with minimal JavaScript overhead.
2. Synced Patterns (formerly Reusable Blocks)
Synced Patterns let you create a block layout once — say, a testimonial card or service grid — and reuse it across multiple pages. Edit the pattern in one place and every instance updates. For agencies managing multi-page sites, this removes a major maintenance headache.
FSE vs. Page Builders: Which Should You Choose?
The honest answer depends on your site's requirements and your team's technical comfort. Here's how we frame it for clients:
Choose FSE/block themes when: You need maximum performance (Lighthouse 95+), you're building a long-lived site that needs to stay on WordPress core, or you're comfortable with a developer-led build process.
Choose Divi or Elementor when: Your marketing team needs to make frequent layout changes without developer support, you need the visual flexibility of a drag-and-drop canvas, or your project timeline doesn't allow for FSE's steeper learning curve.
At Sumit Brands, we build custom WordPress websites on both stacks depending on the brief. For performance-critical projects, we lean FSE. For client-editable marketing sites, we often reach for Divi with custom child themes.
Performance Implications for SEO
This is where FSE genuinely wins. A well-built block theme with no page builder overhead can achieve Lighthouse scores in the 98–100 range with minimal effort. No builder JavaScript, no redundant CSS, no render-blocking scripts. For technical SEO, that matters — Google's Core Web Vitals are a ranking factor, and FSE sites consistently outperform page-builder equivalents on LCP and CLS.
The Catch: It's Still Developer-Driven
FSE's biggest limitation in 2025 is the same as it was in 2022: it's not genuinely non-technical. Creating a custom block theme from scratch requires PHP knowledge and comfort with WordPress internals. The promise of "design your whole site visually" is real, but only if someone technical set up the theme correctly first.
If your agency is selling FSE as a self-service product for non-technical users, ask them to show you a live client who successfully manages the site without developer support. It's possible — but it requires careful scoping.
Bottom Line
Full Site Editing in 2025 is production-ready. It's not the right tool for every project, but for performance-focused, developer-led builds it's the best WordPress stack available. The performance ceiling is higher, the maintenance footprint is lower, and the codebase stays closer to WordPress core — which matters for long-term security and upgrades.
If you're planning a new WordPress build and want an honest assessment of whether FSE fits your project, start a conversation with us.