HTTP status code 402 — Payment Required — has been reserved since 1997 but never had a standard protocol behind it. x402 changes that by defining a header-based flow where any API endpoint can demand payment and any client can fulfill it on-chain. We built the first implementation on Stacks, bringing native micropayments to Bitcoin's programmable layer.The ProblemAPI monetization today means API keys, subscription tiers, rate limiters, billing dashboards, and invoice disputes. All of that inf...
