Shopify Functions vs Cart Transform — what's the difference?
Shopify Functions is Shopify's WebAssembly-based extension platform for customizing checkout logic. It replaces Shopify Scripts. Cart Transform is one function type within the platform — it modifies cart line items. Other Function types: Delivery Customization, Payment Customization, Product Discount, Order Discount, Fulfillment Constraints. Cart Transform is what you use for personalization surcharges and per-option pricing.
Step-by-step setup
- Understand the hierarchy. Functions = platform. Cart Transform = one type.
- Identify your use case. Pricing at cart = Cart Transform. Discount = Discount Function.
- Use an app when possible. Print It My Way handles Cart Transform without custom Function code.
All Shopify Function types
- Cart Transform — modify cart line items (personalization surcharges, bundles, per-character fees)
- Product Discount — apply discounts to specific products
- Order Discount — apply discounts to whole orders
- Shipping Discount — apply shipping discounts
- Delivery Customization — modify delivery options
- Payment Customization — modify payment methods
- Fulfillment Constraints — enforce fulfillment rules
- Validation — enforce checkout validation rules
Which Function type for personalization pricing
Cart Transform. It's the only Function type that can add per-line surcharges. Personalization fees (engraving $8, gift wrap $5, monogram $12) all flow through Cart Transform.
Custom Function vs app
You can write your own Cart Transform Function in Rust or JavaScript. Requires developer time. Or use a product options app that ships Cart Transform functionality out of the box. Print It My Way uses Cart Transform natively for per-character pricing, upcharges, and gift-wrap fees on every tier.
Cart Transform without custom code
Print It My Way ships Cart Transform functionality on every tier.
Install Print It My Way — Free Cart Transform vs variant pricing →Frequently asked questions
Do I need to write custom Function code?
No if a product options app covers your use case. Print It My Way handles Cart Transform for personalization.
Are Shopify Functions Plus-only?
Cart Transform is Plus-native. Non-Plus stores use app-side equivalents that preserve behavior.
Do Functions replace Shopify Scripts?
Yes. Scripts is being deprecated in favor of Functions.
What language do you write Functions in?
Rust or JavaScript — compiled to WebAssembly.
Can I use multiple Functions on the same store?
Yes. Each Function type can have multiple Functions installed.