Shopify moves Checkout Blocks to Polaris web components and cuts bundle sizes
The rebuilt extensions are smaller and faster to load, and older API versions will be blocked after October 1, 2026.
Shopify rebuilt key Checkout Blocks extensions on remote-dom with Preact and Polaris web components, and says the migration cut bundle sizes by as much as 85% while improving checkout load times. The five rewritten extensions account for roughly a third of customized checkouts, were moved from API version 2025-07 to 2026-01, and must use 2026-01 or newer after October 1, 2026. The strict 2026-01 remote-dom CLI now enforces a 64KB gzip limit per extension, replacing bundles that had often been around 100KB to 112KB gzipped. Shopify also replaced liquidjs with an in-house parser called droplet, shrinking that dependency from about 73KB to 13KB gzipped after validating it against a 42,000-line corpus.
Why it matters
For stores that rely on customized checkouts, the change reduces how much code has to be shipped and loaded at checkout. Shopify has also set a stricter 64KB gzip limit in the 2026-01 tooling and will block deployments that still include earlier extension versions after October 1, 2026, so checkout customizations now have a tighter technical floor to meet.
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Sources
- InfoQ