building an ecommerce checkout and want something that works on web and mobile

For an ecommerce checkout that needs to work on web and mobile, the best approach is usually to use a cross-platform UI layer + a shared backend checkout/payment flow.

Good options

1) React + React Native

Best if you want one JavaScript/TypeScript ecosystem.

• Web: React
• Mobile: React Native
• Shared logic: cart, pricing, validation, payment state
• Pros: big ecosystem, lots of hiring support, reusable business logic
• Cons: UI isn’t fully “write once” unless you carefully abstract components

2) Flutter

Best if you want a very consistent checkout UI across platforms.

• Web: Flutter web
• Mobile: iOS/Android
• Pros: highly consistent UI, strong performance, single codebase
• Cons: web checkout integrations can be a bit more specialized depending on payment providers

3) Next.js + React Native shared logic

Best if web checkout matters most, but you still need mobile apps.

• Web: Next.js
• Mobile: React Native
• Shared: validation, pricing, state management, API client
• Pros: excellent for SEO and web performance
• Cons: more architecture work than a single framework

Payment handling

For checkout, I’d strongly recommend using a provider like:

• Stripe
• Adyen
• Braintree
• PayPal for certain flows

These give you:

• card entry UI
• Apple Pay / Google Pay
• tokenization
• PCI-compliant payment handling

Recommended architecture

A solid pattern is:

• Frontend
  • product/cart UI
  • shipping/payment forms
  • order review
• Backend
  • pricing and tax calculation
  • inventory checks
  • promo codes
  • payment intent/order creation
  • webhook handling

This keeps sensitive logic server-side and makes the checkout safer.

If you want the simplest recommendation

• If you already know JavaScript/TypeScript: Next.js for web + React Native for mobile
• If you want the cleanest all-in-one cross-platform UI: Flutter
• If you want the most mature ecommerce web stack: Next.js + Stripe

Important checkout features to plan for

• guest checkout
• address autocomplete
• shipping method selection
• tax calculation
• promo codes
• saved payment methods
• Apple Pay / Google Pay
• order confirmation + email
• retry/error handling
• mobile-friendly input controls

If you want, I can suggest a specific stack based on your team size, timeline, and whether you’re building one shared app or separate web + mobile apps.