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.
Sources & further reading
Primary sources referenced in this article. We link to official platform documentation and standards bodies rather than secondary summaries so you can verify claims directly.