Block Themes and Full Site Editing in 2026: Why Classic Themes Are Fading

Block themes and Full Site Editing spent their first years as the WordPress feature everyone had opinions about and few people shipped with. That era is over. Every default theme since Twenty Twenty-Two has been a block theme, the Site Editor has matured through years of steady releases, and an increasing share of new WordPress builds start from a block theme rather than a classic one. Classic themes are not deprecated and will keep working for a long time, but the direction of the platform is unambiguous. This article explains how block themes actually work, why the momentum shifted, and where classic themes still make sense.

What a block theme actually is

A classic theme is a collection of PHP templates — header.php, single.php, functions.php — that mix markup with template tags and the loop. A block theme replaces that with three ingredients:

• HTML templates made of blocks. Files like templates/single.html contain block markup — the same commented-HTML format the editor produces — instead of PHP. Headers and footers live in parts/ as reusable template parts.
• theme.json. A single configuration file defines the design system: color palette, typography scale, spacing, layout widths, and per-block styling defaults. It replaces hundreds of lines of scattered CSS and the old Customizer options with one declarative source of truth.
• Patterns. Prebuilt block arrangements — heroes, pricing tables, testimonial grids — that users insert and edit freely.

The consequence of this structure is the headline feature: because templates are block markup rather than PHP, users can open any template in the Site Editor and change it visually. The header, the 404 page, the blog archive layout — all editable without touching code or hiring the original developer.

Why the momentum shifted

The tooling caught up

Early Full Site Editing was rough, and developers rightly complained. The intervening releases fixed most of the pain: the Site Editor gained proper navigation and a command palette, style revisions let you roll back design changes, synced patterns replaced reusable blocks with overridable variants, and the Create Block Theme plugin made it practical to design in the editor and export a real, versionable theme. The workflow of building a theme largely inside the editor, then exporting it to files under version control, went from awkward to genuinely pleasant.

Performance by default

Block themes are structurally faster than the average classic theme. WordPress loads only the block styles a page actually uses rather than a monolithic stylesheet, layout and spacing come from generated utility styles instead of framework CSS, and there is no jQuery dependency or theme options framework in the payload. A typical block theme ships dramatically less front-end weight than the multipurpose classic themes that dominated the 2010s, which translates directly into Core Web Vitals headroom.

Less code to maintain

A large share of what classic theme developers wrote by hand — enqueueing Google Fonts, building a Customizer color panel, writing responsive menu JavaScript, registering image sizes — is either declared in theme.json or handled by core blocks. Modern block themes are startlingly small. Less bespoke code means fewer bugs, easier handoffs, and clients who cannot accidentally break the PHP because there barely is any.

The theme.json way of thinking

For developers, the biggest mental shift is moving from writing CSS to declaring design tokens. A fragment illustrates the idea:

{
  "version": 3,
  "settings": {
    "color": {
      "palette": [
        { "slug": "brand", "color": "#0f4c81", "name": "Brand" },
        { "slug": "surface", "color": "#f7f7f5", "name": "Surface" }
      ]
    },
    "typography": {
      "fluid": true,
      "fontSizes": [
        { "slug": "large", "size": "clamp(1.5rem, 3vw, 2rem)", "name": "Large" }
      ]
    }
  }
}

Everything declared here flows through the whole system: the editor shows these exact colors and sizes, blocks render them as CSS custom properties, and global style variations can swap entire palettes site-wide. The discipline pays off in consistency — there is one place design decisions live, and the editor can never drift out of sync with the front end, because they are reading the same file.

What still keeps classic themes alive

An honest assessment has to acknowledge where classic themes remain rational. Enormous existing sites built on classic themes have no business rewriting a working codebase for architectural fashion. Some highly bespoke builds — intricate custom queries, unusual template logic, tightly integrated plugin ecosystems — are still more directly expressed in PHP templates, although hybrid themes (classic themes that adopt theme.json and block templates piecemeal) offer a middle path. Page-builder ecosystems like Elementor operate somewhat parallel to this whole story and continue to serve their audience. And agencies with deep classic-theme expertise and mature starter themes face real retraining costs that they are right to schedule deliberately rather than urgently.

What has genuinely faded is the case for starting a new standard site on a classic theme. The default choice flipped: you now need a specific reason to go classic, where five years ago you needed a specific reason to go block.

Advice for making the move

If you are a site owner, try the Site Editor on a staging copy with a well-built block theme before committing; the editing experience is the product, so evaluate it directly. If you are a developer, start with the Create Block Theme plugin and one real project rather than reading specs: build the design in the editor, export, and study the files it produces. Learn theme.json deeply, because it is the durable skill — hybrid themes, block themes, and even the editor's per-block controls all resolve through it. And keep patterns at the center of client builds, because a good pattern library is what lets non-technical editors assemble on-brand pages without breaking anything.

The bottom line

Full Site Editing took years longer to mature than its early advocates promised, and the skepticism it earned along the way was fair. But in 2026 the verdict is in: block themes are lighter, more maintainable, and more empowering for the people who actually edit sites day to day. Classic themes will keep running for years — WordPress does not break its past — but they are now the legacy path. The platform's present, and clearly its future, is blocks all the way down.