Payment API Comparison 2026

How Payment APIs Work

The typical online card payment flow

Common Use Cases

Why developers need payment APIs

Feature Comparison

Side-by-side comparison of payment processing services

Provider Deep Dives

Detailed breakdown of each payment service

Merchant of Record vs Self-Managed

Who handles tax compliance and liability?

Stripe Tax ($0.50/tx) and TaxJar can add tax automation to self-managed solutions, reducing the gap.

Code Examples

Get started with each payment provider

Create Checkout Session

// Install: npm install stripe
const stripe = require('stripe')('sk_test_...');

// Create a Checkout Session (server-side)
const session = await stripe.checkout.sessions.create({
  mode: 'payment',
  payment_method_types: ['card'],
  line_items: [{
    price_data: {
      currency: 'usd',
      product_data: {
        name: 'Pro Plan',
        description: 'Monthly subscription',
      },
      unit_amount: 2999, // $29.99 in cents
    },
    quantity: 1,
  }],
  success_url: 'https://example.com/success?session_id={CHECKOUT_SESSION_ID}',
  cancel_url: 'https://example.com/cancel',
});

// Redirect customer to session.url
console.log(session.url);

// Install: npm install square
const { Client, Environment } = require('square');

const client = new Client({
  accessToken: 'YOUR_ACCESS_TOKEN',
  environment: Environment.Sandbox,
});

// Create a payment link
const response = await client.checkoutApi.createPaymentLink({
  idempotencyKey: crypto.randomUUID(),
  order: {
    locationId: 'YOUR_LOCATION_ID',
    lineItems: [{
      name: 'Pro Plan',
      quantity: '1',
      basePriceMoney: {
        amount: 2999n, // $29.99 in cents (BigInt)
        currency: 'USD',
      },
    }],
  },
});

console.log(response.result.paymentLink.url);

// Install: npm install @paypal/paypal-server-sdk
const paypal = require('@paypal/paypal-server-sdk');

const client = new paypal.Client({
  clientCredentialsAuthCredentials: {
    oAuthClientId: 'YOUR_CLIENT_ID',
    oAuthClientSecret: 'YOUR_CLIENT_SECRET',
  },
  environment: paypal.Environment.Sandbox,
});

const ordersController = new paypal.OrdersController(client);

// Create an order
const order = await ordersController.ordersCreate({
  body: {
    intent: 'CAPTURE',
    purchaseUnits: [{
      amount: {
        currencyCode: 'USD',
        value: '29.99',
      },
    }],
  },
});

// Redirect to order.result.links[1].href (approval URL)
console.log(order.result.id);

Create Subscription

// Create a recurring price
const price = await stripe.prices.create({
  currency: 'usd',
  unit_amount: 2999,
  recurring: { interval: 'month' },
  product_data: { name: 'Pro Plan' },
});

// Create Checkout Session for subscription
const session = await stripe.checkout.sessions.create({
  mode: 'subscription',
  line_items: [{
    price: price.id,
    quantity: 1,
  }],
  success_url: 'https://example.com/success',
  cancel_url: 'https://example.com/cancel',
});

// Or create subscription directly for existing customer
const subscription = await stripe.subscriptions.create({
  customer: 'cus_...',
  items: [{ price: price.id }],
  payment_behavior: 'default_incomplete',
  expand: ['latest_invoice.payment_intent'],
});

// Install: npm install @paddle/paddle-node-sdk
const { Paddle } = require('@paddle/paddle-node-sdk');

const paddle = new Paddle('YOUR_API_KEY');

// Create a product and price in Paddle dashboard
// Then generate a checkout session:

// Frontend: embed Paddle.js
// <script src="https://cdn.paddle.com/paddle/v2/paddle.js"></script>

// Initialize and open checkout
// Paddle.Initialize({ token: 'YOUR_CLIENT_TOKEN' });
// Paddle.Checkout.open({
//   items: [{ priceId: 'pri_...' , quantity: 1 }],
//   customer: { email: 'user@example.com' },
// });

// Server-side: verify via webhook or API
const subscription = await paddle.subscriptions.get(
  'sub_...'
);
console.log(subscription.status); // active, paused, canceled
console.log(subscription.nextBilledAt);

Webhook Handling

const express = require('express');
const stripe = require('stripe')('sk_test_...');
const app = express();

// IMPORTANT: use raw body for signature verification
app.post('/webhook',
  express.raw({ type: 'application/json' }),
  (req, res) => {
    const sig = req.headers['stripe-signature'];
    let event;

    try {
      event = stripe.webhooks.constructEvent(
        req.body, sig, 'whsec_...'
      );
    } catch (err) {
      return res.status(400).send(`Webhook Error: ${err.message}`);
    }

    switch (event.type) {
      case 'checkout.session.completed':
        // Fulfill the order
        const session = event.data.object;
        console.log('Payment succeeded:', session.id);
        break;
      case 'invoice.payment_failed':
        // Handle failed subscription payment
        console.log('Payment failed for:', event.data.object.customer);
        break;
    }

    res.json({ received: true });
  }
);

const crypto = require('crypto');
const express = require('express');
const app = express();

const WEBHOOK_SIGNATURE_KEY = 'YOUR_SIGNATURE_KEY';

app.post('/square-webhook',
  express.raw({ type: 'application/json' }),
  (req, res) => {
    const signature = req.headers['x-square-hmacsha256-signature'];
    const url = 'https://example.com/square-webhook';

    // Verify signature
    const hmac = crypto.createHmac('sha256', WEBHOOK_SIGNATURE_KEY);
    hmac.update(url + req.body.toString());
    const expected = hmac.digest('base64');

    if (signature !== expected) {
      return res.status(403).send('Invalid signature');
    }

    const event = JSON.parse(req.body);

    if (event.type === 'payment.completed') {
      const payment = event.data.object.payment;
      console.log('Payment completed:', payment.id);
      console.log('Amount:', payment.amountMoney.amount);
    }

    res.status(200).send('OK');
  }
);

Pricing at Scale

Estimated monthly processing fees by revenue volume

Estimates assume $50 average transaction, domestic US cards only. International cards, currency conversion, chargebacks, and instant payouts add additional fees. Adyen excluded (custom enterprise pricing). At $500K+/mo, all providers offer volume discounts on request. MoR fees include tax handling that would otherwise cost $100-500+/mo separately.

Which Payment API Should You Use?

Quick decision guide based on your business type

Frequently Asked Questions