swap-integration

Use the Uniswap Trading API with its 3-step flow: POST /check_approval, POST /quote, then POST /swap. Because the API does not support browser CORS preflight, proxy requests through your dev server or platform rewrites, and add the Buffer polyfill for viem.

Use the Trading API for frontends, backends, and bots since it handles routing optimization automatically. Use the Universal Router SDK when you need direct control over transaction construction, and call the Universal Router contract directly for smart contract integrations.

The error usually means the quote was wrapped in a quote field instead of spread into the request body, or permitData was included for a UniswapX route. Spread the quote response directly and strip permitData for DUTCH_V2, DUTCH_V3, and PRIORITY routes.

Not directly, because the API rejects CORS preflight OPTIONS requests with 415 Unsupported Media Type. You must proxy requests through your own server using Vite dev proxy, Next.js rewrites, Vercel rewrites, or Cloudflare Pages redirects.

On L2 chains like Base, Optimism, and Arbitrum, swaps outputting ETH often deliver WETH because the UNWRAP_WETH command is not always included. Check the WETH balance after the swap and call withdraw on the WETH contract to unwrap it.

The API allows roughly 10 requests per second per endpoint. Implement exponential backoff with jitter for 429 responses, add 100-200ms delays between sequential calls, and cache approval check results to reduce request volume.