# Payment protocols

There are 6 payment protocols in the index.

6 agent wallets. Also on the [web page](https://agentwalletindex.fyi/global/online/category/payment-protocols).

## Agent wallets

1. [Agent Payments Protocol (AP2)](https://agentwalletindex.fyi/global/online/agent-payments-protocol-ap2.md), Payment protocols, Online: Open protocol for agent-executed payments: signed intent, cart and payment mandates give an auditable trail from the user's instruction to the payment.
2. [Agentic Commerce Protocol (ACP)](https://agentwalletindex.fyi/global/online/agentic-commerce-protocol-acp.md), Payment protocols, Online: Open standard connecting buyers, AI agents and businesses for programmatic checkout. The delegated-payment spec passes a scoped, single-use payment token to…
3. [ATXP](https://agentwalletindex.fyi/global/online/atxp.md), Payment protocols, Online: Agent Transaction Protocol from Circuit & Chisel: agents discover, negotiate and pay other agents over HTTP with per-call micropayments.
4. [L402](https://agentwalletindex.fyi/global/online/l402.md), Payment protocols, Online: HTTP 402 payment flow from Fewsats: a server answers with priced offers, the client pays the gateway by card, bank transfer or Lightning, then retries for the…
5. [Machine Payments Protocol (MPP)](https://agentwalletindex.fyi/global/online/machine-payments-protocol-mpp.md), Payment protocols, Online: Open protocol that standardizes HTTP 402 for machine-to-machine payments with challenges, credentials and receipts. Co-authored by Tempo and Stripe and…
6. [x402](https://agentwalletindex.fyi/global/online/x402.md), Payment protocols, Online: Open HTTP 402 payment standard: a server answers 402 with payment terms, the client signs a payload, retries, and settles on chain. Rail-agnostic; USDC on Base…

## Other categories in Online

- [Agent wallets](https://agentwalletindex.fyi/global/online/category/agent-wallets.md): 8 agent wallets
- [Payments platforms](https://agentwalletindex.fyi/global/online/category/payments-platforms.md): 8 agent wallets
- [Key management](https://agentwalletindex.fyi/global/online/category/key-management.md): 5 agent wallets
- [Card rails](https://agentwalletindex.fyi/global/online/category/card-rails.md): 2 agent wallets

> **Check before you fund.** Features, fees and protocol support change. Follow the cited source on each row before you let an agent hold or spend money.