x402

Open standard for internet-native payments built on HTTP 402, letting APIs and agents pay per request across crypto and fiat networks.

Category: Protocols
Website: https://x402.org
Repository: https://github.com/x402-foundation/x402
Docs: https://docs.x402.org
Status: active
Pricing: open-source
License: Apache-2.0
Maintainer: x402 Foundation
Added: 2026-10-02
Updated: 2026-10-02
Last verified: 2026-10-02
Submitted by: agentica-curator

Description

Server middleware declares prices per route; clients pay and retry inside the HTTP request flow, with no accounts or checkout pages. Reference SDKs exist for TypeScript (@x402/*), Python (pip install x402) and Go. The canonical repo is x402-foundation/x402 (coinbase/x402 is now a fork).

Agent access

llms.txt: https://docs.x402.org/llms.txt
Auth: none

Coinbase CDP x402 Facilitator: Coinbase Developer Platform's x402 offering: a hosted facilitator that verifies and settles x402 payments, plus seller and buyer SDK quickstarts.
Machine Payments Protocol (MPP): Open standard for machine-to-machine payments over HTTP 402, co-developed by Tempo and Stripe; charge per API request, tool call or content.
L402 (Lightning HTTP 402): Lightning Labs standard for paying for and authenticating to APIs with Bitcoin Lightning payments; Aperture is the reference reverse proxy.
Coinbase Agentic Wallet: Wallet tooling that lets AI agents hold, spend, trade and earn stablecoins with guardrails, via the awal CLI + skills or an MCP server.

Guides & comparisons

Pay for an API as an agent with x402 (Guide): How an agent pays per request for an HTTP API or MCP tool with x402 v2, from reading the 402 response to signing a USDC payment with spend caps, on testnet first.
Agent payment protocols compared (Comparison): x402, MPP, L402, ACP, AP2 and UCP compared on what each standardizes, payment rails, wire format, governance, spec status and SDKs, so you can tell machine-payment protocols from agent-checkout protocols.
Agent that can buy things (Stack): The pieces for an agent that pays for APIs per call with x402 stablecoins and buys from merchants with controlled virtual cards, with spend limits, proof of user intent and a full audit trail.
Pay with x402 (Skill): Read an x402 v2 402 response, check it against a spending policy, pay with an SDK or CLI, and verify the PAYMENT-RESPONSE receipt.

Sources

Machine-readable

JSON
Markdown
Source file on GitHub (edit via pull request)