If you're on Shopify Plus and your checkout relies on Scripts, you have a deadline very close at hand: on June 30, 2026, Shopify Scripts stop running. Shopify has confirmed this date won't move again. Their replacement is Functions, and the change goes much further than a fresh coat of paint on the syntax. Here's what you need to understand, and what's actually at stake.
What happens on June 30, 2026
Scripts were bits of Ruby code that ran at checkout time, reserved for Plus stores, to customize discounts, shipping or payment. Shopify is retiring them. Since April 15, 2026, you can already no longer create or edit them. On June 30, they stop completely.
If you do nothing, all your custom logic that went through Scripts disappears at once. An automatic discount resets to zero. A B2B customer who saw their wholesale price reverts to the public price. Shipping customized per segment falls back to the default config. The checkout doesn't crash, but it starts applying the wrong rules, which is sometimes worse because it goes unnoticed.
What Functions are
A Function is code compiled to WebAssembly that runs directly inside Shopify's infrastructure, at precise points in the buying journey. The difference from Scripts is architectural. Where a Script was Ruby interpreted in a sandbox, a Function is a compiled binary that runs natively, in under 5 milliseconds, even on a Black Friday.
To put it simply: it's faster, more reliable, and it takes the load without flinching. You write your logic, you compile it, you deploy it via the Shopify CLI, and it runs at the core of the platform rather than as an overlay.
What you can do with them
Functions cover the main use cases that went through Scripts, and then some:
- Custom discounts: conditional promotions, complex carts, logic that native discounts can't express.
- Custom shipping: hide, rename or reorder methods based on the cart, the customer or the destination.
- Payment: filter or reorder payment methods based on business rules.
- Cart and checkout validation: block an order that doesn't meet your conditions (minimum quantity, forbidden product mix, and so on).
Not everything is a word-for-word translation of the old Script. The Functions API has its own logic, and some cases call for rethinking the implementation rather than copying it over.
Function or app: how to choose
That's the real question for a merchant. A store app solves plenty of needs without writing a line of code, but it adds weight and an external dependency, as I explain in my article on the real impact of Shopify apps.
A custom-coded Function, on the other hand, does exactly what you need, with no overlay, and runs inside the Shopify infrastructure. You choose it when your logic is specific to your business, when no app truly fits, or when you want full control over how your checkout behaves. For the rest, a good app often stays the simplest choice, and I give a selection in the best Shopify apps.
Handling the migration without breaking your checkout
Good news: Scripts and Functions can coexist on the same store during the transition. So you can migrate brick by brick instead of switching everything over at once the night before the deadline.
The approach I apply: list every active Script and what it really does, identify the equivalent Function (or app, when that's more relevant), reimplement, test under real conditions, then disable the old Script once the Function is validated. The classic mistake is underestimating the scale of the work: rewriting each piece of logic and testing it takes time. Better to get to it before June 30 than to discover a broken checkout in the middle of a weekend.
Why it matters beyond the deadline
Even once the migration is done, Functions remain the right tool for customizing a Shopify checkout cleanly. Shopify is clearly betting on them for the future of the platform, and it's the ground where a developer makes the difference: precise business logic, fast, that doesn't slow your store down and depends on no third-party app.
It's exactly the kind of work I step in on. If you're not sure what your Scripts are still running, or if you want to replace three apps with one clean Function, my audit covers the question and hands you a concrete action plan. You can also see the kind of projects I deliver in my portfolio section.
