0x

Provides trading APIs for token swaps, gasless transactions, cross-chain routing, and trade analytics across multiple blockchains and liquidity sources.

The 0x API uses api key authentication; has freemium pricing; offers a free tier (Free account available; start building for free); rate limits: 5 requests per second on Standard plan; Custom plans support 100+ RPS. Verified 2026-07-08 with per-field source links.