Spree Storefront (Next.js)

The Spree Next.js storefront is a separate application that talks to the Spree backend over the v3 Store API. It’s hosted at github.com/spree/storefront and cloned separately into your project tree.

The storefront is optional. Headless deployments may use a custom frontend — React Native, Astro, Remix, or hand-rolled. Spree’s job is to expose a clean API; what consumes it is your choice. This skill assumes the official Next.js storefront, but the API contract is identical for any frontend.

How it connects to Spree

Browser ──HTTPS──> Next.js storefront ──API──> Spree backend (Rails)
                          │
                          └── @spree/sdk for typed API calls

The storefront authenticates against the Spree backend via a publishable API key (pk_… prefix). Customer-bound operations (their cart, their account) use additional auth — JWT for logged-in customers, cart tokens for guest carts.

# .env.local — server-side only (the storefront makes all API calls via Server Actions)
SPREE_API_URL=http://localhost:3000
SPREE_PUBLISHABLE_KEY=pk_…

@spree/sdk — the canonical client

Don’t hand-write fetch calls. Use @spree/sdk for typed access to the Store API:

import { createClient } from '@spree/sdk'

const spree = createClient({
  baseUrl: process.env.SPREE_API_URL!,
  publishableKey: process.env.SPREE_PUBLISHABLE_KEY!,
})

// List products
const { data, meta } = await spree.products.list({
  expand: ['media', 'default_variant'],
})

// Get a single product by slug or prefixed ID
const product = await spree.products.get('cool-shirt')

// Create a cart
const cart = await spree.carts.create()

// Add item to cart — cart ID positional, token via options.spreeToken
await spree.carts.items.create(cart.id, {
  variant_id: 'variant_k5nR8xLq',
  quantity: 1,
}, { spreeToken: cart.token })

The SDK includes:

• Full TypeScript types generated from the Spree serializers (Product, Order, Cart, etc.)
• Runtime Zod schemas in @spree/sdk/zod if you want validation
• Automatic retry with exponential backoff
• Ransack query param transformation
• Webhook signature verification in @spree/sdk/webhooks

Authentication modes

The customer login flow:

const { token, refresh_token, user } = await spree.auth.login({
  email: 'jane@example.com',
  password: 'secret',
})

// Pass the JWT per request via options.token
const orders = await spree.customer.orders.list({}, { token })
const me = await spree.customer.get({ token })

// Refresh later
const { token: newToken } = await spree.auth.refresh({ refresh_token })

Channels — which sales surface

If the merchant has multiple channels (website, mobile app, in-store POS), the storefront should identify which one it represents. Set the channel via the SDK config:

const spree = createClient({
  baseUrl: process.env.SPREE_API_URL!,
  publishableKey: process.env.SPREE_PUBLISHABLE_KEY!,
  channel: 'online',         // channel code; or prefixed ID like 'ch_…'
})

The Spree backend uses Spree::Current.channel to scope queries — only products published on that channel surface in API responses. If channel is omitted, the store’s default channel is used.

Common storefront patterns

Server-rendered PDP

// app/products/[slug]/page.tsx
import { spree } from '@/lib/spree'

export default async function ProductPage({ params }: { params: { slug: string } }) {
  const product = await spree.products.get(params.slug, {
    expand: ['default_variant', 'variants', 'media', 'categories'],
  })

  return (
    <main>
      <h1>{product.name}</h1>
      <img src={product.media?.[0]?.large_url ?? undefined} alt={product.media?.[0]?.alt ?? ''} />
      <AddToCartButton variantId={product.default_variant_id} />
    </main>
  )
}

The v3 Store API uses flat responses — product.name, not product.data.attributes.name. Related records appear as either ID fields (e.g. default_variant_id) or, when expanded, as nested objects (e.g. product.default_variant, product.media[]).

Client-side cart

Carts are server-state, so use SWR or React Query. The cart ID + token persist in a cookie:

'use client'
import useSWR from 'swr'

export function MiniCart({ cartId, token }: { cartId: string; token: string }) {
  const { data: cart } = useSWR(
    ['cart', cartId],
    () => spree.carts.get(cartId, { spreeToken: token })
  )
  if (!cart) return null
  return <span>{cart.items.length} items</span>
}

Checkout

The Store API exposes payment sessions for the checkout flow — a single, provider-agnostic endpoint that works with any session-based gateway (Stripe, Adyen, PayPal); the provider is selected via payment_method_id. The pattern:

1. Customer hits checkout — POST /api/v3/store/carts/:cart_id/payment_sessions with a payment method choice (cart token in X-Spree-Token header).
2. Backend returns a session with provider-specific data (Stripe Checkout URL, Adyen drop-in token, etc.).
3. Storefront redirects to the provider OR renders the provider’s embedded form.
4. Customer completes — provider posts back to the Spree backend, which fires payment_session.completed events.
5. Storefront calls spree.carts.paymentSessions.complete(cartId, sessionId, { session_result: 'success' }, options) once the customer confirms, then spree.carts.complete(cartId, options) to get the Order — or relies on the provider webhook, in which case the backend completes the cart → order transition automatically.

The spree_stripe / spree_adyen / spree_paypal_checkout gems ship reference checkout flows. Don’t roll your own unless you’re integrating a new provider.

Webhook handling

For Next.js storefronts, @spree/sdk/webhooks provides HMAC signature verification with typed event payloads:

// app/api/webhooks/spree/route.ts
import { verifyWebhookSignature, type WebhookEvent } from '@spree/sdk/webhooks'

export async function POST(req: Request) {
  const body = await req.text()
  const signature = req.headers.get('x-spree-webhook-signature') ?? ''
  const timestamp = req.headers.get('x-spree-webhook-timestamp') ?? ''

  if (!verifyWebhookSignature(body, signature, timestamp, process.env.SPREE_WEBHOOK_SECRET!)) {
    return new Response('Invalid signature', { status: 401 })
  }

  const event: WebhookEvent = JSON.parse(body)
  switch (event.name) {
    case 'order.completed':
      await sendCustomThankYouEmail(event.data)
      break
    case 'order.shipped':
      await pushShippingNotification(event.data)
      break
  }

  return Response.json({ received: true })
}

The Spree backend ships outbound webhooks as Spree::WebhookEndpoint records. Configure URL + events under Settings → Webhooks in the admin.

Storefront vs backend — where does the change belong

The rule: anything customer-visible is the storefront. Anything that touches data, money, or business logic is the backend. When in doubt, backend — keeping logic centralized makes it consistent across all frontends if you ever ship a second one.

Common gotchas

• Don’t ship secret keys to the browser. Only publishable keys (pk_…) belong in NEXT_PUBLIC_* env vars. Secret API keys (sk_…) are server-side only.
• Cart tokens are not credentials — they identify a cart, not a user. But they grant cart access, so treat them like a session token: HTTPS only, set as an httpOnly cookie when possible.
• Cache aggressively but invalidate on cart/auth changes. Product catalog can sit in CDN; cart calls must always hit fresh.
• Pricing displayed must match what the API will charge. Don’t compute totals client-side. Always pull the cart’s total from the API after add/remove operations — the backend applies promotions, taxes, shipping rules.
• i18n is the storefront’s job. The Store API returns translated strings based on the x-spree-locale header (or a locale query param) — not Accept-Language. Set it via the SDK: createClient({ ..., locale }) for a default, or pass { locale } in per-request options; the SDK sends it as x-spree-locale.

Where to read further

• SDK docs: node_modules/@spree/docs/dist/developer/sdk/quickstart.mdx (also at https://spreecommerce.org/docs/developer/sdk/quickstart)
• Storefront docs: node_modules/@spree/docs/dist/developer/storefront/nextjs/architecture.mdx, customization.mdx, deployment.mdx
• Storefront tutorial: node_modules/@spree/docs/dist/developer/tutorial/api.md, sdk.md
• Storefront source: https://github.com/spree/storefront — reference implementations for product listing, cart, checkout, account pages