Payment Protocols
The two major agent payment protocols in production.
x402
HTTP 402 Payment Protocol
x402 is an open internet-native payment standard that revives the dormant HTTP 402 'Payment Required' status code, enabling direct blockchain-based transactions over HTTP.
MPP
Machine Payments Protocol
MPP is an internet payment protocol for machine-to-machine commerce. It uses the HTTP 402 status code to signal payment requirements, supporting both crypto (on-chain stablecoins) and fiat (cards, wallets via Stripe). Developed by Stripe and Tempo.
Comparison
| Feature | x402 | MPP |
|---|---|---|
| Payment Type | On-chain stablecoin | Fiat + stablecoin |
| Settlement | Instant (on-chain) | Session-based |
| Auth Flow | HTTP 402 → payment → access | HTTP 402 → session → payment → access |
| Currencies | USDC | USD, USDC, USDT |
| Backed By | Coinbase, Cloudflare | Stripe, Tempo |