Automatic CSS subsetting for `{% stylesheet %}` tags
Shopify developer change
MerchantDiff detected this entry in Shopify's official developer changelog on April 23, 2026.
This Shopify update is categorized as Action Required, Themes, Update.
What changed
Shopify is introducing CSS content subsetting for {% stylesheet %} tags to improve storefront performance. Starting April 20, 2026, Shopify only delivers the CSS from {% stylesheet %} tags that are relevant to the sections, blocks, and snippets rendered on each page, instead of serving all {% stylesheet %} CSS on every page load. What this means for your theme If your theme's CSS classes are self-contained – each file's {% stylesheet %} only styles HTML elements within that same file or its direct children (rendered via {% render %}) – no changes are needed. Your theme is already compatible. However, if a file's {% stylesheet %} defines CSS classes that are used by HTML elements in other, unrelated files, those styles may not be included on pages where the defining file isn't rendered.
Who is affected
Apps and storefronts using the affected Storefront API surface should review this change.
What action may be needed
Review the official Shopify entry and test the affected integration. Apply any required code or configuration changes before deploying.
Use the official Shopify entry below as the source of truth for technical implementation details, affected APIs, migration instructions and deadlines.
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