Global retail eCommerce reached $6.8 trillion in 2025, representing 8.3% year-over-year growth, and the businesses capturing that growth aren't relying on monolithic platforms. They're assembling specialized services through APIs—connecting tools for payments, shipping, inventory, search, tax, and marketing into cohesive commerce stacks.

An eCommerce API is a programmatic interface that lets your online store connect to external services—payment processors, shipping carriers, search engines, and tax calculators—through standardized request/response patterns. Instead of building every capability in-house, you integrate specialized services that handle specific functions better than any monolithic platform could.

This approach, often called composable commerce, gives development teams the flexibility to swap components, scale individual services, and avoid vendor lock-in. This guide covers 12 APIs across core eCommerce functions, with real features and use-case guidance so you can evaluate which ones belong in your stack.

1. Stripe API

The dominant payment API for developer-first teams. Stripe handles payment processing, subscriptions, invoicing, fraud detection (Radar), and multi-currency support through a clean, well-documented RESTful API. It powers checkout for millions of businesses from startups to enterprises.

Key Features

• Payment processing across cards, digital wallets (Apple Pay, Google Pay), BNPL, and bank transfers
• Stripe Billing for subscriptions, metered billing, and usage-based pricing
• Stripe Radar for ML-powered fraud detection analyzing hundreds of signals per transaction
• Stripe Connect for marketplace split payments with configurable payout schedules
• Prebuilt UI components (Elements, Checkout, Payment Links)
• Support for 135+ currencies and local payment methods across eight payment method families
• Webhooks with HMAC signature verification
• SDKs for Python, Node.js, Ruby, PHP, Java, Go, and .NET

Quick Integration Example

// Create a payment intent with Stripe
const paymentIntent = await stripe.paymentIntents.create({
  amount: 2000,
  currency: 'usd',
  payment_method_types: ['card'],
});

Best For

• Developer-first teams wanting maximum API flexibility and documentation quality
• SaaS and subscription businesses needing metered or recurring billing
• Marketplaces needing split payments and seller payouts via Stripe Connect
• Businesses selling internationally requiring multi-currency support
• Teams needing automated sales tax compliance through Stripe Tax

2. Adyen API

Unified commerce platform handling online payments, in-store POS, and platform payments through a single API integration. Adyen processes payments for brands like Spotify, Uber, eBay, and Microsoft. It's stronger than Stripe in European and APAC markets with direct acquiring in 30+ countries, reducing cross-border fees and improving authorization rates. Adyen's ML-powered RevenueAccelerate delivers 1.4-1.43% improvement in authorization rates.

Key Features

• Single integration for online, in-app, and in-store payments via Terminal API
• Local acquiring in 30+ countries—reduces cross-border interchange fees
• RevenueAccelerate: ML-powered authorization optimization
• Built-in Protect risk engine with configurable fraud prevention rules
• PCI DSS v4.0.1 Level 1 Service Provider certification with SOC 2 Type 2 compliance
• Support for 32 globally available payment methods
• Tap to Pay SDKs turning iOS and Android devices into payment terminals
• Backend SDKs for Java, .NET, Node.js, PHP, Python, Ruby; Mobile SDKs for iOS, Android, React Native, Flutter

Best For

• Brands with omnichannel needs (online + physical retail)
• Companies with significant European, APAC, or Latin American customer bases where local acquiring matters
• High-volume merchants focused on maximizing authorization rates
• Businesses wanting unified online and in-store payments

3. PayPal REST API

PayPal's REST API is the required integration path for all new implementations, having replaced legacy SOAP/NVP APIs. The platform provides checkout via JavaScript SDK v6, Orders v2 API, Subscriptions v1 API, and Payouts API supporting 96 countries and 24 currencies. With 436-438 million active accounts globally, PayPal remains a trusted payment option recognized by buyers worldwide.

Key Features

• PayPal Checkout via JavaScript SDK v6 with dynamic button customization
• Orders v2 API and Payments v2 API for complete transaction lifecycle management
• Subscriptions API v1 with vault tokens for secure recurring charges
• Payouts API supporting batch payments up to 15,000 per API call across 96 countries
• Dispute and refund management endpoints
• Venmo integration for US customers through Braintree SDK

Best For

• Stores wanting PayPal as an additional checkout option alongside a primary processor
• B2B and subscription businesses utilizing tokenized recurring payments
• US-focused stores wanting Venmo checkout through Braintree's SDK
• Marketplaces needing global payment disbursement
• Merchants targeting global demographics across 200+ countries

4. Shopify Storefront and Admin APIs

Shopify's two core APIs power the largest eCommerce API ecosystem. The Admin API manages the backend—products, orders, customers, inventory, fulfillment. The Storefront API enables headless commerce, letting you build any custom frontend while Shopify handles the commerce engine.

The Storefront API is 100% GraphQL with no REST alternative in version 2026-01, while the Admin API maintains REST fallback for legacy integrations but prioritizes GraphQL. Shopify Functions extends backend logic for custom checkout, discount, delivery, and payment rules through WebAssembly-based customization.

Key Features

• Admin API: full CRUD for products, orders, customers, inventory, fulfillment, and analytics
• Storefront API: build custom buyer-facing experiences against Shopify's backend
• Shopify Functions: customize checkout validation, discounts, delivery options, and payment logic
• Webhooks with up to 8 retries over 4 hours for event-driven integrations
• GraphQL-first design with cost-based rate limiting (100-2,000 points/second depending on tier)
• Hydrogen framework for building custom Shopify storefronts in React with SSR support
• Oxygen hosting with 300+ global points of presence

Best For

• Brands wanting full storefront customization while keeping Shopify's checkout and fulfillment infrastructure
• Developers building Shopify apps using GraphQL-first architecture
• Businesses wanting proven commerce backend without managing infrastructure
• Teams exploring headless CMS architecture paired with Shopify's APIs

5. Medusa.js API

Open-source headless commerce engine built for developers who want full control. Medusa provides a modular, API-first commerce backend—products, carts, orders, payments, fulfillment—that you own and self-host. Think of it as a composable alternative to Shopify for teams that don't want vendor lock-in. REST API with a JavaScript SDK and plugin architecture under the MIT license.

Key Features

• Fully open-source under MIT license—complete source code access with no vendor lock-in
• Modular architecture: swap payment, fulfillment, and notification providers independently
• Multi-region and multi-currency support with region-specific pricing and tax rules
• Support for B2B, subscriptions, marketplace, and DTC use cases without tier restrictions
• Plugin system for extending functionality via npm packages
• Self-hosted or deployable on any cloud provider
• First-class Next.js starter and admin dashboard
• No transaction fees, no platform subscription, unlimited admin users

Best For

• Developer teams seeking complete technical control with self-hosted deployments
• Organizations prioritizing vendor lock-in avoidance through MIT-licensed platforms
• Businesses requiring headless commerce without API rate limits or proprietary restrictions
• Teams building custom commerce experiences requiring full source code modification

Note: Medusa.js doesn't offer native GraphQL support—developers requiring GraphQL need custom resolvers or a middleware translation layer.

6. Shippo API

Multi-carrier shipping API connecting your store to 85+ carriers (USPS, UPS, FedEx, DHL, and regional carriers) through a single REST integration. Shippo handles rate comparison, label creation, tracking, address validation, customs documentation, and returns with discounted shipping rates through pre-negotiated carrier agreements.

Key Features

• Multi-carrier rate comparison in a single API call across 85+ carriers
• Discounted shipping rates when using Shippo's carrier accounts
• Batch label creation processing up to 10,000 shipments per asynchronous API request with webhook notifications
• Real-time package tracking with status updates
• Address validation and autocorrection
• Automated customs forms and country-specific compliance documents (EEL/PFC, B13A, EORI)
• Sandbox environment for testing

Best For

• SMBs and mid-market stores shipping physical products domestically and internationally
• Businesses wanting to compare rates across multiple carriers with pre-negotiated discounts
• International sellers needing automated customs documentation
• Teams leveraging asynchronous batch processing for large shipment volumes

7. Amazon Selling Partner API (SP-API)

Amazon's Selling Partner API (SP-API) is the modern REST/JSON API that replaced the deprecated Marketplace Web Service (MWS) as of December 31, 2023. SP-API features OAuth 2.0 authorization, sandbox testing environments, and Restricted Data Tokens (RDTs) for accessing sensitive buyer information. The API covers the complete Amazon seller lifecycle: order management, FBA inventory tracking, product listings, fulfillment, pricing, and real-time notifications.

Key Features

• Order management: create, track, fulfill, and cancel orders programmatically
• FBA inventory management with inbound shipment creation and multi-marketplace visibility
• Listing creation and catalog operations via Listings Items API
• Competitive pricing and Buy Box data through Pricing API
• Notifications API for real-time event subscriptions via webhooks, EventBridge, or SQS
• Reports API for sales, inventory, and performance data exports
• Sandbox environment with static and dynamic testing modes

Best For

• Any business selling on Amazon Marketplace needing automation
• Brands using FBA needing inventory sync between Amazon and their own storefront
• Multi-channel sellers managing Amazon alongside Shopify or other platforms
• Developers building Amazon seller tools or integration middleware

8. Algolia API

AI-powered search and discovery API purpose-built for eCommerce. Algolia delivers 1-20ms search response times with typo tolerance, three types of faceted filtering (conjunctive, disjunctive, and hierarchical), AI-powered product recommendations, and merchandising rules. InstantSearch frontend libraries support JavaScript, React, and Vue. REST API with comprehensive documentation.

Key Features

• 1-20ms search response times via distributed infrastructure with automatic geographic routing
• Typo tolerance using Damerau-Levenshtein distance with configurable thresholds
• Three faceted filtering types: conjunctive (AND), disjunctive (OR), and hierarchical
• AI Recommend API with bought-together, related-products, trending-products, and custom models
• Merchandising rules: pin, boost, bury, hide products, or display banners per query
• Analytics dashboard tracking search conversion, click-through, and no-result rates
• InstantSearch frontend libraries for React, Vue, and vanilla JavaScript

Best For

• Stores with large catalogs (1,000+ SKUs) where sub-20ms response times improve conversion
• Businesses wanting AI-powered recommendations for cross-sell and upsell
• Headless commerce builds needing standalone search decoupled from the commerce platform
• Teams wanting merchandising control without engineering effort

9. TaxJar API (by Stripe)

TaxJar provides RESTful API with comprehensive sales tax calculation for all U.S. jurisdictions, featuring rooftop-accurate rate determination, automated nexus monitoring, and deep Stripe integration following 2021 acquisition. TaxJar handles US multi-state sales tax, EU VAT, Canadian GST/PST, and Australian GST. AutoFile service offers automated filing with state-specific implementations.

Key Features

• Real-time tax calculation via POST /taxes endpoint with rooftop-accurate rate determination
• Nexus tracking and economic nexus determination with state-specific thresholds
• International VAT/GST support for EU, UK, Canada, and Australia
• Product tax categorization through comprehensive tax code library
• AutoFile: automated sales tax return preparation and filing for enrolled US states
• Stripe integration via Stripe Tax's Tax Complete plan
• Transaction reporting and audit-ready records

Best For

• US-based businesses selling across multiple states needing sales tax nexus compliance
• International sellers needing multi-jurisdiction tax calculation
• Companies wanting to automate tax filing and reporting
• Stripe users wanting seamless tax + payments integration

Note: TaxJar tracked 400+ local sales tax rate changes in 2025—automated updates are critical for compliance.

10. Akeneo PIM API

Product Information Management (PIM) platform providing REST API with OAuth 2.0 authentication for centralizing, enriching, and distributing product data across all sales channels. Akeneo manages product attributes, categories, media assets, and translations with automated data quality scoring (A-E rating system), then syndicates to Shopify, Adobe Commerce, Salesforce Commerce Cloud, SAP Commerce Cloud, and partners like Productsup and Lengow. Modern Event Platform provides real-time webhooks with "at least once" delivery guarantee.

Key Features

• Centralized product data management: descriptions, specs, categories, SKUs, and custom attributes
• Multi-channel syndication to major eCommerce platforms and marketplaces
• Media asset management for product images, videos, and documents
• Multi-locale and translation support for international catalogs
• Data quality scoring (A-E scale) tracking enrichment completeness
• Workflow rules for product enrichment and approval
• REST API with Event Platform for real-time product update notifications
• Symfony-based Extension SDK for custom component development

Best For

• Brands with large catalogs (500+ products) selling across multiple channels
• Teams where product data is fragmented across spreadsheets, ERPs, and platform admin panels
• Businesses pairing Strapi for editorial content with Akeneo for structured product data
• Companies needing to syndicate consistent product information to 5+ sales channels

11. Klaviyo API

Email and SMS marketing automation platform built specifically for eCommerce. Klaviyo's REST API enables real-time sync of customer profiles, order events, browse behavior, and product catalogs to power automated flows and hyper-segmented campaigns through OAuth 2.0 authentication. Features tiered rate limiting from 1-350 requests/second depending on account tier, hundreds of prebuilt eCommerce integrations, and predictive analytics including customer lifetime value.

Key Features

• Real-time event tracking via Track & Identify APIs: product viewed, added to cart, order placed
• Automated email and SMS flows triggered by customer behavior with conditional splits
• Dynamic product recommendations and personalized content blocks
• Advanced segmentation based on purchase history, browse behavior, RFM scoring, and predictive analytics
• Back-in-stock, price-drop, and low-inventory notifications
• Customer lifetime value and predicted next order date accessible via API
• Webhook system with HMAC-SHA256 signature verification

Best For

• DTC and eCommerce brands focused on retention and lifecycle marketing
• Stores wanting behavior-triggered automation rather than basic newsletters
• Teams needing eCommerce-native segmentation and predictive analytics
• Businesses wanting clear revenue attribution per email/SMS flow

12. HubSpot CRM API

Free CRM with a REST API for basic eCommerce customer data integration and sales/marketing workflows through native eCommerce platform connections. HubSpot manages contacts, companies, deals, tickets, and custom objects. However, the free tier is capped at 2,000 contacts and 100 products maximum, requiring the Professional tier ($890/month) for realistic eCommerce catalog sizes. Shopify integration provides one-way sync only—HubSpot serves as a read-only order repository. API rate limits of 110 requests per 10 seconds per account apply to OAuth integrations.

Key Features

• Contact and company management with unlimited custom properties
• Deal pipeline and lifecycle stage tracking
• Custom objects for eCommerce-specific data models
• Marketing email, automation workflows, and lead scoring integration
• Webhooks for real-time CRM updates
• Free tier supporting up to 2,000 marketing contacts and 100 products maximum
• Native integrations with Shopify, WooCommerce, BigCommerce, Stripe

Best For

• Early-stage eCommerce startups with under 100 SKUs who need free CRM functionality
• Teams wanting to connect customer data from Shopify, WooCommerce, or BigCommerce to sales and marketing workflows
• Businesses needing basic customer lifecycle tracking without specialized eCommerce marketing tools like Klaviyo

Limitation: HubSpot's free tier caps products at 100—most eCommerce catalogs will require the Professional tier ($890/month) which supports 10,000 products.

How to Choose the Right eCommerce APIs for Your Stack

You won't use all 12 of these APIs—but you'll likely need 4-6 working together. The right combination depends on your commerce platform, business model, and where you're selling.

Start With Your Commerce Engine

If you're on Shopify, your core commerce API is set—supplement with specialized services: payments (Stripe or Adyen), search (Algolia), shipping (Shippo), tax (TaxJar), and marketing automation (Klaviyo).

If you're going fully headless with Strapi as your content layer, you need a commerce engine underneath. The Shopify Storefront API provides managed infrastructure with proven reliability. Medusa.js offers complete technical control through its MIT license, direct PostgreSQL database access, and zero transaction fees—appealing to teams prioritizing vendor independence.

Match APIs to Your Growth Stage

Just launching: Stripe + Shopify provide core payment and commerce infrastructure. Add Shippo for shipping, then layer in Klaviyo for customer engagement and retention from day one.

Scaling (multi-channel): As your catalog grows, add Algolia for search optimization, TaxJar for multi-state tax compliance, and Akeneo for product data consistency across channels. If expanding to Amazon, SP-API provides marketplace integration.

Enterprise / composable build: Adyen for unified commerce across online and physical retail, complemented by Medusa.js or Shopify Storefront for headless commerce. Akeneo for PIM, HubSpot for customer lifecycle management.

Evaluate Integration and Architecture Fit

Check REST vs. GraphQL support—Shopify mandated GraphQL for new public apps as of April 2025, while BigCommerce, WooCommerce, and Adobe Commerce use REST as their primary architecture.

Prioritize APIs with webhook support for event-driven architectures. Consider data residency requirements for EU customers.

Ensure your APIs can communicate: Stripe + TaxJar are natively integrated, Shopify has prebuilt connectors for most services listed here, and Klaviyo offers hundreds of prebuilt integrations.

In a composable commerce architecture, Strapi serves as the content and experience layer—managing product marketing content, landing pages, and editorial alongside commerce data. This separation lets each tool do what it's best at. Learn more about Strapi's approach to headless commerce and explore what's new in Strapi 5.

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