What Shopify Functions are
A Function is a small program compiled to WebAssembly that Shopify runs inside its own infrastructure during cart and checkout. Shopify passes it the cart data it asks for and applies what it returns: a discount, a hidden payment method, a validation error.
Any plan can use public App Store apps that contain Functions. Only Shopify Plus stores can use custom apps that contain Function APIs. That's where my work usually starts: logic unique to your business that no public app covers.
The Function APIs I build with
Discount
Product, order and shipping discounts in one Function: tiered pricing, BOGO, VIP rules.
Delivery and payment customization
Rename, reorder or hide shipping and payment options.
Cart and checkout validation
Block checkout with a clear message when a cart breaks a rule.
Cart transform, fulfillment and routing
Bundles, fulfillment constraints and order routing for multi-location brands.
How a custom Function project runs
From rules to release
Native and apps first
Check native discounts, order value limits and shipping settings, then well-reviewed public apps. Custom work is for what's left.
Rules in plain English
Every condition, every exception, and what the customer sees. Most delays come from undefined edge cases, not code.
Merchandiser controls
Thresholds, product lists and messages live in metafields, metaobjects or app settings, so your team changes rules without a code deploy.
Test and maintain
Large carts, B2B buyers, Shop Pay and draft orders tested. Functions target an API version, so I plan for updates.
How to work together
Custom Functions usually fit in a focused sprint.
Shopify Plus
Plus & Checkout Sprint
For: Shopify Plus brands
A focused sprint on checkout and Shopify Functions.
What's included
- Checkout Extensibility
- Shopify Functions for discounts, shipping and payments
- Shopify Scripts to Functions migration
- Pricing
- Per sprint
- Price
- $4,500 (2 weeks)
FAQ
Common questions
Can I use Shopify Functions without Shopify Plus?
Yes, through public apps from the Shopify App Store, which work on any plan. Custom apps containing Function APIs require Plus.
Can Functions change product prices directly?
Not the way Scripts did. Functions apply price changes through discounts or cart transforms, so some pricing logic needs a different design.
What language are Functions written in?
Any language that compiles to WebAssembly. Shopify provides Rust and JavaScript tooling and recommends Rust for performance on large carts.
Do Shopify Scripts still work?
No. Shopify deprecated Scripts on June 30, 2026, and any Scripts still published were deactivated.
Keep reading
Related specialties and guides
Related specialties
Shopify Checkout Expert
Checkout Extensibility, checkout UI extensions and the move from Scripts to Functions.
Shopify Apps & Integrations Expert
Custom apps and Admin/Storefront API integrations with ERPs, 3PLs and more.
Shopify Plus Expert
Deciding on Plus, then putting its features to work.
