x402 settles in USDC. 2s supports two rails — Base and Solana — at the same dollar price. The 402 envelope advertises both; your client pays on whichever chain it holds USDC.
On Base, payment is an EIP-3009 transferWithAuthorization: you sign an off-chain authorization for the quoted USDC amount and the facilitator submits it. You need a small USDC balance on Base and an EVM wallet key.
On Solana, payment is a partially-signed SPL token transfer of USDC. You need USDC on Solana and a Solana wallet key. In the Python SDK, install the 2sio[svm] extra to enable it.
You do not choose up front — the 402 response lists every accepted rail in its accepts array, and your client signs for the one it can. Same price either way. Gas/transaction fees are paid by the facilitator; you only need USDC.
Call a live x402 API right now — no signup.
Browse the full endpoint directory, grab the quickstart, or read the llms.txt manifest. Every endpoint is keyless and pay-per-call.