Carbon Fields is the code-first custom-fields library for WordPress. Unlike ACF or SCF, there is no admin UI for registering fields. Developers declare containers and fields in PHP through the Carbon_Fields\Container and Carbon_Fields\Field classes inside carbon_fields_register_fields. The fields render on post edit screens, term edit screens or options pages, and their values write to wp_postmeta with the _-prefixed keys Carbon configures.

SleekPixel reads the registered Carbon containers at runtime and exposes each as a separate template scope. A 'Post Meta' container on the 'post' post type with fields for subtitle, cover image, and read time can each feed template slots by their Carbon field name. The share card pulls field values through carbon_get_post_meta()-equivalent reads, so theme code and SleekPixel see the same data.

The 1200 by 630 PNG lands in uploads on every post save. The SEO plugin's og:image filter publishes the URL into the post head, and scrapers see a card that reflects Carbon's field values on every post update.

Carbon Fields exists because some teams prefer to declare custom fields in PHP rather than through an admin UI. The advantage is that the field schema lives in version control, ships in deploys and stays in sync across environments. The trade-off is that off-the-shelf OG image plugins typically depend on the ACF UI or expose mappings through a settings page that does not see Carbon-registered fields.

SleekPixel bridges the gap. The plugin reads Carbon's runtime container registry, so per-container share cards work without copying field schemas into a settings UI. Teams that picked Carbon Fields for the code-first workflow get share cards that respect the same workflow.

The share card uses the same field reads as theme code, so a designer who can call carbon_get_post_meta() can describe the share card. The cost is one license. The benefit is per-container share previews on every Carbon-powered post URL.