Shopify's Ruby Liquid Engine and LiquidJS Differ Enough to Break Live Storefronts

Shopify's storefront renders Liquid templates using its own Ruby-based engine, while most local development tools — including Shopify Theme Check and Node-based simulators — use LiquidJS, a separate JavaScript reimplementation. The two engines agree on most syntax but diverge on whitespace handling, particularly around trimming markers like {%- and -%}, which can produce different output. This discrepancy becomes critical when rendered whitespace is treated as data, such as when splitting strings on delimiters to build table rows, SVG paths, or JSON blobs. A developer documented how a size chart metafield rendered correctly in local preview but broke on the live storefront due to this mismatch. The recommended approach is to use local linting for syntax and schema validation, but always verify whitespace-sensitive output directly on a Shopify dev store or theme preview.