Checkout UI Extensions & Shopify Functions in Action: How We Customized the Checkout for Saudi Arabia’s Leading Medical Apparel Brand

Following a transition period throughout 2025, the January 1, 2026 enforcement deadline for Saudi Arabia’s new shipping regulations created a decisive turning point for global e‑commerce. The mandate required every parcel to include a valid National Address Short Code. Our goals were to:

• Achieve 100% compliance with Saudi transport authority requirements.

• Eliminate carrier rejections and failed deliveries caused by missing or invalid Short Codes.

• Keep the checkout experience fast, secure, and friction‑free for customers.

• Utilise Shopify’s modern composable stack (UI Extensions & Functions) rather than deprecated scripts.

When the regulation hit, Medical Outfit found themselves stuck. Shopify’s standard checkout wasn't built to handle Saudi‑specific validation, leading to:

• Shipping Dead‑Ends – Carriers refused to pick up parcels without the Short Code.

• The "Correction Tax" – Fixing addresses manually after orders were placed was costing teams hours of support time.

• Customer Friction – Buyers were confused about where to enter their code, leading to abandoned carts.

• No real‑time validation – Invalid codes could not be caught until after the order was submitted.

We didn't just add a text box; we built an intelligent, two‑part system using Shopify’s modern extensibility stack. Rather than relying on deprecated checkout.liquid scripts or hacky workarounds, we delivered two native Shopify components:

1. Checkout UI Extensions for the frontend customer experience.

2. Shopify Functions (Validation capability) for backend enforcement.

This approach guaranteed compatibility with all future Shopify updates, eliminated external server dependencies, and kept the checkout lightning‑fast. The entire integration, from API connection to production deployment, was completed in just 7 days.

Layer 1: The Intelligent Checkout Widget (Checkout UI Extension)
We built a custom UI Extension using React and Shopify’s UI Extension API, integrated directly into the checkout delivery step:

• Real‑Time Validation – As the customer types, the widget checks the Short Code format instantly.

• One‑Click Address Completion – Through an authoritative Saudi National Address API, a valid Short Code automatically populates the city, street, and building number.

• Fully Localized – The experience shifts seamlessly between Arabic and English, providing helpful prompts in the user's native language.

• Buyer Journey Intercept – The extension prevents checkout progression if the Short Code is invalid, guiding the customer to correct it.

Layer 2: The Backend Guardian (Shopify Function)
To catch any edge cases (draft orders, bots, or API glitches), we implemented a server‑side "Safety Net" using a Shopify Function written in Rust (compiled to WebAssembly):

• The Function leverages Shopify’s validation capability to inspect every order before the "Pay Now" button is activated.

• If the Short Code is missing or malformed, it prevents order completion and provides clear instructions on how to fix it.

• This places the validation logic on the server, making it immune to client‑side tampering.

Graceful Failure Handling
We ensured the checkout still works if the external API has a momentary outage, with cached fallback validation rules to never block a legitimate sale.

y turning a regulatory hurdle into a high‑tech checkout feature, Medical Outfit saw immediate improvements:

• Failed deliveries dropped to near‑zero for address‑related issues.

• Support volume saw a dramatic reduction in "Where is my package?" inquiries.

• Fulfillment speed improved – orders are now "Ready to Ship" immediately upon purchase.

• 100% compliance with Saudi transport authority requirements.

• The store is now future‑proof, fully migrated away from deprecated checkout scripts.