Stripe On-Ramp Tutorial

Use Stripe's Crypto On-Ramp API to let users buy USDC on Polygon directly inside your app. You'll create an on-ramp session on the backend and render Stripe's hosted widget on the frontend.

You will achieve:

Create a Stripe Crypto On-Ramp session via API
Pass client_secret securely to the frontend
Render a live fiat-to-Polygon USDC purchase widget

Security notice

All examples below are demonstrations only.
In production, never expose STRIPE_SECRET_KEY or private wallet keys in client code — store them in a secure vault or secrets manager.

Overview

Stripe's Crypto On-Ramp lets users convert fiat (e.g., USD) to supported crypto assets such as USDC on Polygon.

Requirements

A US-based business entity (excluding Hawaii)
Stripe account
On-Ramp feature enabled (automatically appears after compliance verification)
API key (sk_test_… or sk_live_…)

Reference docs

Schema

name	type	required	example	description
destination_currency	string	✅	`"usdc"`	The target crypto asset
destination_network	string	✅	`"polygon"`	Blockchain network
wallet_address[0][type]	string	✅	`"self_custody"`	Type of wallet
wallet_address[0][address]	string	✅	`"0xYourPolygonAddress"`	Destination wallet address
STRIPE_SECRET_KEY	string	✅	`"sk_test_..."`	Your Stripe API key (server-side only)

Create Session cURL

Run this on your backend server only (never in a browser):

curl https://api.stripe.com/v1/crypto/onramp_sessions \
  -u sk_test_your_secret_key: \
  -d destination_currency=usdc \
  -d destination_network=polygon \
  -d wallet_addresses[0][type]=self_custody \
  -d wallet_addresses[0][address]=0xYOUR_POLYGON_ADDRESS

If successful, Stripe returns a JSON response containing a client_secret:

{
  "id": "cos_0MYvmj589O8KAxCGp14dTjiw",
  "object": "crypto.onramp_session",
  "client_secret": "cos_0MYvmj589O8KAxCGp14dTjiw_secret_BsxEqQLiYKANcTAoVnJ2ikH5q002b9xzouk",
  "created": 1675794053,
  "livemode": false
}

Bun / NodeJS backend

import Stripe from "stripe";
const stripe = new Stripe(process.env.STRIPE_SECRET_KEY);

export async function createOnrampSession(req, res) {
  const session = await stripe.crypto.onramps.sessions.create({
    destination_currency: "usdc",
    destination_network: "polygon",
    wallet_addresses: [
      { type: "self_custody", address: "0xYOUR_POLYGON_ADDRESS" }
    ],
    // optional: customer, email, reference
  });
  res.json({ client_secret: session.client_secret });
}

Serve to Frontend

Pass only the client_secret to your client app — never your Stripe secret key.

<script src="https://js.stripe.com/v3/crypto/onramp.js"></script>
<div id="onramp"></div>

<script>
(async () => {
  // Fetch client_secret from your backend
  const { client_secret } = await fetch("/api/create-onramp-session").then(r => r.json());

  const onramp = await window.StripeOnramp.init({
    clientSecret: client_secret,
    appearance: {
      theme: "light", // optional UI customization
    },
  });

  onramp.mount("#onramp");
})();
</script>

Users can now buy USDC on Polygon directly from your site.

The funds are sent to the wallet specified in your onramp_session.

Extra

Debugging, sanity checks, and guardrails.

Do / Don't Do Guardrails

✅ Do	❌ Don't
Store API keys in a vault, not in code	Hardcode `STRIPE_SECRET_KEY` in frontend
Use Stripe Sandbox first	Test with live key before compliance is cleared
Log only non-sensitive session info	Log full `client_secret` values

Errors

code	meaning	fix
403_access_denied	Onramp not enabled	Wait for compliance review
400_invalid_wallet_address	Bad or unsupported wallet	Verify address format
401_unauthorized	Wrong API key	Use correct/test or live key

Quick Checklist

Backend has STRIPE_SECRET_KEY set
Frontend only receives client_secret
Wallet address is valid on Polygon
Tested in Sandbox before production

Stripe On-Ramp Tutorial

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