Shopify Scripts reached their hard sunset in June 2026. Every piece of custom checkout and discount logic now has to run on Shopify Functions, the compiled runtime that executes in under 5ms (Digital Applied, Jun 28, 2026). If you never migrated, your checkout logic broke this month. The good news is that Shopify Functions is not a tax you pay to survive. It is an upgrade that makes your checkout faster and, done right, lifts your conversion rate.
The deadline already passed
June 2026 was the final sunset for Shopify Scripts. There is no extension. All custom checkout customizations, discount logic, and payment or shipping rules that used to run on Scripts must now run on Shopify Functions (Digital Applied, Jun 28, 2026).
For brands that migrated early, this is a non-event. For brands that did not, the risk is quiet and expensive: discounts that no longer apply, checkout rules that no longer fire, and revenue leaking on every session with no error message to warn you.
Why founders read this wrong
Here is where most founders get it backwards. They treat the migration as a compliance chore, something to survive and forget. That framing costs them.
Shopify Functions run on a compiled runtime with execution under 5ms (Digital Applied, Jun 28, 2026). Compared to the older Scripts model, that means faster checkout performance and linear scalability when traffic spikes during a promo or a viral moment. The migration you resented is the reason your checkout can hold up at peak load. The forced upgrade is not a cost. It is a conversion advantage you were handed.
How to make Shopify Functions work for you
Confirm every customization actually migrated
Do not assume. Inventory every discount, bundle, shipping rule, and payment customization you ever built, then verify each one runs on Functions now. The silent failures are the dangerous ones.
Pressure-test at your highest traffic hour
Functions scale linearly, but you only know your checkout holds if you test it under load. Simulate or observe your busiest hour before your next sale, not during it.
Use the speed as a selling point internally
A checkout that executes discount logic in under 5ms is a checkout that does not stall the shopper at the last step. Faster, more reliable checkout is one of the clearest levers on conversion. Treat this migration as the moment you claimed that lever.
Align checkout with your wider stack
If you run Shopify alongside marketplaces, a clean checkout is only one piece. Our [shopify amazon integration](#) work keeps your DTC and marketplace operations consistent, our [Amazon growth services](#) keep your listings aligned, and our [growth retainer](#) manages the whole stack so a checkout change does not break something downstream.