Guide

Web2 Bridge

Round up fiat and traditional payments into crypto investments via the REST API.

Overview

Not every payment happens on Solana. The Web2 Bridge lets you record round-ups from fiat transactions — credit card purchases, Stripe payments, invoices — and accumulate them in a Buff wallet for auto-investment into crypto.

REST API Approach

Send a POST request to the round-up endpoint with the transaction value. Buff calculates the round-up and records it against the API key's associated wallet.

roundup.sh
bash
1curl -X POST https://sow-beryl.vercel.app/api/roundup \
2  -H "Content-Type: application/json" \
3  -H "x-api-key: your-key" \
4  -d '{"txValueUsd": 4.73, "plan": "sprout"}'

The response includes the round-up breakdown:

response.json
typescript
1{
2  "roundUpUsd": 0.27,
3  "userInvestmentUsd": 0.2679,
4  "buffFeeUsd": 0.0021,
5  "accumulatedUsd": 3.42,
6  "thresholdUsd": 5.00,
7  "skipped": false
8}

API Parameters

FieldTypeDescription
txValueUsdnumberThe fiat transaction amount in USD
planstringRound-up plan: "sprout", "growth", or "oak"
sourcestringOptional tag (e.g. "stripe", "shopify")
userIdstringOptional user identifier for multi-user platforms

Stripe Webhook Pattern

The most common Web2 integration is listening for Stripe payment events and recording round-ups for each successful charge.

stripe-webhook.ts
typescript
1import Stripe from "stripe"
2
3// In your webhook handler (e.g. /api/webhooks/stripe)
4export async function POST(req: Request) {
5  const event = stripe.webhooks.constructEvent(
6    await req.text(),
7    req.headers.get("stripe-signature")!,
8    process.env.STRIPE_WEBHOOK_SECRET!,
9  )
10
11  if (event.type === "charge.succeeded") {
12    const charge = event.data.object as Stripe.Charge
13    const amountUsd = charge.amount / 100
14
15    // Record the round-up via Buff REST API
16    await fetch("https://sow-beryl.vercel.app/api/roundup", {
17      method: "POST",
18      headers: {
19        "Content-Type": "application/json",
20        "x-api-key": process.env.BUFF_API_KEY!,
21      },
22      body: JSON.stringify({
23        txValueUsd: amountUsd,
24        plan: "sprout",
25        source: "stripe",
26        userId: charge.customer as string,
27      }),
28    })
29  }
30
31  return new Response("ok")
32}

Use Cases

  • –E-commerce: round up every Stripe/Shopify checkout into BTC savings
  • –SaaS: round up subscription payments for your users automatically
  • –Invoicing: round up freelancer payments when invoices are paid
  • –POS systems: round up in-store purchases via your payment processor webhook

Fiat On-Ramp with Changelly

Users can fund their Buff wallet directly with fiat currency using Changelly. No business entity required — just create an account and embed. Users buy SOL with credit card, it deposits directly into their Buff wallet. From there, round-ups auto-invest into chosen assets.

onramp-link.ts
typescript
1// Generate a Changelly buy link for a user's Buff wallet
2const buyUrl = "https://changelly.com/buy/sol?to=" + buffWalletAddress;
3
4// Open in new tab or embed
5window.open(buyUrl, "_blank");

Email Signup Flow

For users who don't have a Solana wallet yet, the Buff Dashboard supports an email-based signup flow. Users provide their email address, and a Buff wallet is derived deterministically from their credentials. Once signed up, they can fund via MoonPay and start accumulating round-ups immediately — no browser extension or seed phrase required.

  • –User enters their email on the Buff signup page
  • –A unique Buff wallet is derived and associated with the account
  • –User funds the wallet using the MoonPay on-ramp widget
  • –Round-ups accumulate and auto-invest into BTC, ETH, or other assets
  • –The wallet private key can be exported at any time to a standard Solana wallet
Note
The REST API is rate-limited to 100 requests per minute per API key. For high-volume integrations, batch round-ups or contact us for increased limits.