How to Build a Crypto Payment Gateway with Swaps

Crypto payments are no longer experimental. Stablecoin transaction volume hit $33 trillion in 2025 — a 72% increase over the prior year — and USDC alone accounted for $18.3 trillion of that volume. On the merchant side, 46% of surveyed merchants have already integrated cryptocurrency payment options, driven by faster settlement, lower fees, and cross-border reach. The crypto payment gateway market is projected to grow from $2 billion in 2025 to $2.39 billion in 2026 , a 19% year-over-year increase. The core problem: customers want to pay with whatever token they hold. Merchants want to receive stablecoins. A crypto payment gateway bridges that gap by accepting any token and auto-converting it to USDC or USDT at settlement. This guide shows you how to build a non-custodial crypto payment gateway in TypeScript that accepts any ERC-20 token on any supported chain and auto-converts it to stablecoins using swapapi.dev — a free DEX aggregator API covering 46 EVM chains with no API key requir