What these tools are for
The x402 protocol revives the long-dormant HTTP 402 Payment Required status code so that any web request can be priced and paid in stablecoins — no accounts, no API keys, no checkout redirect. It's the plumbing behind machine-to-machine and agentic payments: software that can make an HTTP request can also pay for it.
That power comes with fiddly details — base-unit amounts, token decimals, the exact shape of a 402 challenge body. These tools exist to remove that friction so you can ship a paywall in minutes instead of debugging integer math at 2am. Everything here is free, requires no signup, and runs entirely in your browser — nothing you type is ever sent to a server.
Which tool do I need?
- Setting up a paywall or pricing an endpoint? Start with the 402 Response Builder to generate the challenge body and copy server/client code.
- Need the right integer amount for a price? The Base-Unit Converter turns
$0.01into10000(and back) for any token's decimals. - Choosing a protocol or looking for libraries? Browse the x402 directory or compare payment protocols.
Frequently asked questions
Are these tools really free?
Yes — completely free, no account, no rate limits. They're built and maintained by mpp.best, the directory of machine payment protocols, as a resource for the x402 developer community.
Do you store or see what I enter?
No. Every tool runs client-side in your browser. Wallet addresses, amounts and JSON you paste never leave your device.
What is HTTP 402 / x402?
402 Payment Required is a reserved HTTP status code. x402 defines a standard JSON body and header convention for it, letting a server charge for a request inline using on-chain stablecoins. See the x402 overview.
Will you add more tools?
Yes. This hub grows over time with focused utilities for x402 and onchain payments. Suggestions are welcome via the directory.