shopify-theme-development

Create a Liquid section that loops over section.blocks with a {% schema %} defining block types like title, price, variant picker, and buy buttons. Include a presets array so the section appears in the theme editor's Add section menu, and add {{ block.shopify_attributes }} to every block wrapper.

POST to /cart/add.js with a JSON items array, then fetch /cart.js separately to get the true cart state and update the count badge with cart.item_count. Relying only on the add response can leave the badge out of sync.

The section is missing a presets array in its {% schema %} block. Sections without presets are only usable inside JSON templates and never appear in the theme editor's Add section panel.

The img_url filter is deprecated. Use image_url with an explicit width parameter, combined with image_tag, widths, and sizes to generate responsive srcset attributes served from Shopify's CDN.

Preload the hero or product featured image in the head with a link rel=preload tag, inline critical CSS in a style tag, defer non-critical CSS with the media=print onload pattern, and load JavaScript with the defer attribute.

Yes, theme app extensions let apps provide blocks that merchants place through the theme editor. Generate one with shopify app generate extension --type theme_app_extension and define settings in the block's schema.