App SDK Guide

Build apps that work with any Fez store

OAuth 2.0 Flow

Merchant clicks 'Install' in App Store

Fez redirects to redirect_url with authorization code

Your app exchanges code for access_token

Use token to access the API

Scopes

Scope	Access
read_products	Product catalog, variants, inventory
write_products	Create, update, delete products
read_orders	Order list, details, status
write_orders	Update order status, add notes
read_customers	Customer profiles and addresses
read_store	Store info, settings, policies
write_store	Update store settings

App Types

Frontend Apps

Script Tags & App Blocks in the storefront

Backend Apps

Webhooks + API for data processing

Example: Upselling App

// 1. Listen for order.created webhook
app.post("/webhooks/order", async (req, res) => {
  const order = req.body.data;
  
  // 2. Fetch related products via Fez API
  const products = await fez.products.getRelated(order.items);
  
  // 3. Send upsell email to customer
  await sendUpsellEmail(order.customer.email, products);
  
  res.json({ ok: true });
});