Cowrie Research

x402

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x402

  • Name: x402
  • URL: https://www.x402.org/
  • Category: HTTP-native payments protocol / agentic payments standard / API monetization infrastructure
  • Tags: ethereum-ecosystem solana-ecosystem
  • Summary: x402 is the clearest HTTP-native paid-request grammar in the corpus. It standardizes a 402 Payment Required challenge/retry flow with signed payment payloads and optional facilitators. The point is the request syntax, not whichever wallet or settlement venue happens to sit underneath it.
  • What it does:
    • Lets a server return 402 Payment Required with machine-readable payment requirements for a resource
    • Lets a buyer or agent sign a payment payload and retry the request with a payment header so access can be granted programmatically
    • Defines an optional facilitator role that can verify payloads, sponsor execution, and keep sellers from running chain-specific backend infrastructure themselves
    • Supports multi-network and multi-scheme execution through CAIP-style network identifiers, EVM-oriented flows, Solana support, and reference SDKs
    • Has adjacent directory/discovery work, but the durable thing here is still the paid-request handshake itself
  • Key claims:
    • The official site and foundation repo describe x402 as an open standard rather than a Coinbase-only product
    • The docs explicitly frame the protocol around paid API calls, digital resources, and agent-to-agent commerce without account creation or subscription overhead
    • The protocol keeps the transport HTTP-native instead of inventing a separate proprietary session layer
    • Coinbase Developer Platform currently appears to be the most mature hosted facilitator surface, but that is an implementation layer, not the protocol itself
    • Bazaar shows x402 is also growing a discovery layer around the core paid-request flow
  • Whitepaper: Yes. The official x402 technical whitepaper was saved locally as ../../whitepapers/x402-whitepaper.pdf; current primary-source notes are in ../../whitepapers/x402-primary-sources-2026-04-27.md.
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