The “best” payment API depends on your business model, countries, and how much customization you need. For most internet businesses, these are the top choices:

1) Stripe

Best for: SaaS, marketplaces, subscriptions, startups, online platforms
Why people like it:

• Excellent developer experience and documentation
• Strong support for subscriptions, billing, invoices, and marketplaces
• Wide range of payment methods and global coverage
• Easy to get started, but still scales well

Watch out for:

• Can be more expensive than some alternatives
• Account holds/risk reviews can happen for some business types

2) PayPal / Braintree

Best for: Consumer-facing businesses, businesses that want trusted checkout brands
Why people like it:

• Huge brand recognition and user trust
• Easy for customers who already have PayPal accounts
• Braintree supports cards, wallets, and recurring billing

Watch out for:

• Developer experience is usually not as clean as Stripe
• Disputes/chargebacks and account limitations can be frustrating

3) Adyen

Best for: Larger businesses, enterprise, global e-commerce
Why people like it:

• Very strong global payment coverage
• Good for omnichannel and enterprise-scale operations
• Advanced fraud and optimization tools

Watch out for:

• More enterprise-oriented; not always the simplest for small startups
• Often better once you have meaningful volume

4) Checkout.com

Best for: Global digital businesses, marketplaces, higher-volume merchants
Why people like it:

• Good international payment acceptance
• Strong performance and customization
• Useful for companies scaling across regions

Watch out for:

• Typically best suited to established businesses
• Pricing and onboarding can be less startup-friendly than Stripe

5) Square

Best for: Businesses that sell online and in-person
Why people like it:

• Strong if you also have POS/in-person sales
• Simple setup
• Good for small businesses

Watch out for:

• Less ideal for highly customized online payment flows
• Global coverage is not as broad as some competitors

6) Authorize.net

Best for: Businesses wanting a long-established gateway
Why people like it:

• Mature and widely supported
• Works with many merchant accounts and processors

Watch out for:

• Developer experience can feel dated
• Often less attractive than newer APIs unless you need legacy compatibility

7) Paddle / Lemon Squeezy

Best for: SaaS, digital products, software sellers Why people like it:

• Often handles tax/VAT and compliance-related complexity for you
• Good for selling software globally
• Merchant-of-record model can simplify operations

Watch out for:

• Less control over the payment stack
• Fees can be higher, but you save on tax/compliance overhead

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How to choose

Pick based on your business needs:

• SaaS/subscriptions: Stripe, Paddle
• Marketplaces/platforms: Stripe, Adyen, Checkout.com
• Enterprise/global scale: Adyen, Checkout.com
• Small business/simple setup: Square, PayPal
• Digital products / tax simplicity: Paddle, Lemon Squeezy

Key factors to compare

• Supported countries and currencies
• Subscription and recurring billing support
• Marketplace/payout features
• Fraud prevention and chargeback tools
• Checkout conversion and supported payment methods
• API quality and documentation
• Fees, settlement timing, and reserve policies
• Tax handling and compliance responsibilities

If you tell me:

1. your business type,
2. your target countries, and
3. whether you need subscriptions or one-time payments,

I can recommend the best 2–3 APIs for your specific case.