theme.json is the whole theme now
Most of what used to live in functions.php and a pile of PHP templates now belongs in one JSON file. That is a bigger deal than it sounds.
For a long time, “theme development” meant PHP templates, a functions file that grew without
bound, and a build step to make the CSS behave. theme.json collapses a surprising amount of that
into declarative configuration — color palettes, spacing scales, typography presets, block
supports — read directly by the block editor and the front end alike.
The part worth writing about properly is where the line still is: what genuinely belongs in
theme.json now, and what still needs a template part or a block variation to do the job. That
line moved twice in the last year alone.
Longer write-up with real examples coming.
Full-stack developer and WordPress architect writing about headless CMS, Next.js and AI-assisted builds.
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