Shopify Functions vs Shopify Scripts: 2026 Comparison

Two technologies, one job: custom checkout logic. Shopify Scripts did it for eight years. Shopify Functions does it now, and the two barely resemble each other under the hood.

If you're trying to understand what actually changed, not just that something changed, this is the side-by-side comparison.

What was Shopify Scripts?

Shopify Scripts were small Ruby programs, exclusive to Shopify Plus, that ran inline during checkout to customize line item pricing, shipping rates, and payment method visibility. Merchants or developers wrote or pasted code directly into the Script Editor app. No app installation, no separate deployment, just Ruby that executed against the cart at checkout. Scripts launched in 2016 and, for years, were the only way to build custom discount logic Shopify didn't offer natively.

That simplicity was also the constraint. Scripts were locked to Plus stores, required Ruby knowledge, and ran in a sandboxed environment that Shopify's own documentation describes as increasingly unable to keep pace with the platform's checkout extensibility direction. Shopify's developer changelog announcing the final deprecation confirms the two-stage timeline that ended the technology: editing froze April 15, 2026, and execution stopped completely June 30, 2026.

What is Shopify Functions?

Shopify Functions are compiled WebAssembly modules, distributed as part of an installed app, that run custom backend logic across discounts, shipping, payment, and cart behavior on Shopify's own infrastructure in under 5 milliseconds. Instead of pasting Ruby into an editor, a developer builds a Function using Rust, JavaScript, or TypeScript, compiles it with Shopify CLI, and ships it inside an app. Merchants install that app and configure the Function through the Shopify admin, no code required on their end. Shopify's general discounts framework documentation describes Functions as the mechanism for extending app code directly into checkout, creating discount functionality that isn't offered out of the box.

Functions are available on every Shopify plan, not just Plus, which alone represents a meaningful shift. Shopify's transitioning guide frames the difference plainly: Functions are more user-friendly and accessible because they're distributed as apps rather than requiring direct code interaction from the merchant.

Shopify Functions vs Scripts: the core differences

The two technologies differ on five fronts that actually matter to a merchant: plan access, performance, distribution model, coding requirement, and longevity, and Functions wins on all five.

• Plan access. Scripts were Plus-exclusive. Functions-based apps work on every Shopify plan.

• Performance. Scripts had no guaranteed execution speed and could bottleneck during high-traffic events. Functions execute in under 5 milliseconds on Shopify's own infrastructure, a number confirmed directly in Shopify's Function API documentation.

• Distribution. Scripts lived in one store's Script Editor, copy-pasted per store. Functions ship inside apps, installed once and reusable across every store that installs that app.

• Coding requirement. Scripts required Ruby knowledge from whoever maintained them. Functions require Rust or JavaScript to build from scratch, but no code at all if you use a Functions-based app.

• Longevity. Scripts are dead. Editing froze April 15, 2026, and execution stopped entirely on June 30, 2026. Functions are Shopify's active, ongoing extensibility platform with new capabilities added regularly, including expanded POS support added after the discount function framework matured.

Which discount classes does each technology cover?

Shopify Scripts covered three narrow areas, line item pricing, shipping rate manipulation, and payment method visibility, while Shopify Functions expands that into six extension types: Cart and Checkout Validation, Cart Transform, Delivery Customization, Discount, Fulfillment Constraints, and Payment Customization. The Discount Function API alone, documented in full by Shopify, spans three discount classes, product, order, and shipping, in a single unified schema. That means one Function can simultaneously reduce an order total and delivery cost, something Scripts couldn't do without separate, uncoordinated logic for each.

Comparison table: Shopify Scripts vs Shopify Functions

Do you need a developer to use Shopify Functions?

Only if you're building a genuinely custom Function from scratch. For standard discount logic, tiered pricing, BOGO, shipping rules by country, a free no-code app already has the Function built and gives you a visual way to configure it. This is the detail that gets lost in most Scripts-to-Functions coverage, which tends to assume every migration means hiring an agency. Independent migration audits of Plus stores consistently find the same pattern: most Scripts, once actually reviewed, map to standard discount, shipping, or eligibility logic that an existing app already covers.

Flowly: Discount Functions is one such app. It replaces the custom-code step with a visual canvas of Start, Condition, and Apply Discount nodes, covering three discount classes (product, order, shipping), four actions (Percentage Off, Fixed Amount Off, Free Shipping, Buy X Get Y), and 12 combinable conditions. For a store that ran two or three straightforward Scripts, that's the whole migration, no Rust, no WebAssembly, no developer invoice.

FAQ

Can I still write custom Shopify Functions myself?

Yes, if your store is on a plan that supports custom app development, generally Shopify Plus for full flexibility. You'll need Shopify CLI and either Rust or JavaScript compiled to WebAssembly, per Shopify's build-a-discount-function tutorial.

Do Shopify Functions cost money to use?

Functions themselves are free to build and run. Whether you pay depends entirely on the app delivering the Function, some are free, some are paid, same as any Shopify App Store category. Shopify's own Discount Apps built on Shopify Functions collection lists dozens of options spanning both free and paid pricing models.

Is there a cap on how many Functions can run on one store?

Yes, 25 active discount functions per store, and every function runs independently with no awareness of the others. Selection strategies control what happens when more than one could apply.

What happened to merchants who didn't migrate before June 30, 2026?

Their Scripts-based logic simply stopped executing, with no warning banner and no rollback option. Checkout continued processing orders, just without the discount, shipping, or payment customization that Script used to apply. Merchants can still review what was running through the Shopify Scripts customizations report in their admin, which auto-generates a list of what needs rebuilding.

Do Functions and Scripts share the same execution order at checkout?

No, and this matters if you're mid-migration. Functions execute according to Shopify's documented function execution order, which is distinct from how Scripts used to sequence against cart calculation. Testing a rebuilt rule against a live cart before deactivating the old Script is the safest way to confirm behavior matches.

The technology changed completely, but the outcome most merchants actually need, custom discount logic without hiring a developer for every rule, is more accessible now than it was under Scripts. Download Flowly directly from the Shopify App Store to see that in practice, or book a call with Subscribfy's team if your store's post-Scripts checkout strategy needs a broader look.