x402 is an open standard built on HTTP 402 Payment Required that lets developers and AI agents pay for APIs, services, and software with stablecoins over HTTP.

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Location PART 2 - FOUR HIDDEN CHIMNEYS CHAPTER 10: BUILDING-BLOCK REALITY New Rails on the Block

"x402 is an open standard built on HTTP 402 Payment Required that lets developers and AI agents pay for APIs, services, and software with stablecoins over HTTP."

Coinbase's launch announcement defines x402 as an open standard leveraging HTTP 402 Payment Required for stablecoin payments and explicitly names developers and AI agents as users.

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Source title Introducing x402: a new standard for internet-native payments

Source authors Erik Reppel; Nemil Dalal; Dan Kim

Source year 2025

Confidence high

Importance high