More and more of your traffic isn't people. It's software — AI assistants, agents, and crawlers — reading your content or calling your API on someone's behalf. Today you usually have two options, and both are bad: block that software and lose the reach, or serve it for free and earn nothing.
x402 is a third option: let the software pay you a small amount per request, automatically. This post explains what that means in plain terms — no crypto or networking background needed. (Want the engineering detail? See the technical deep dive.)
The simple idea
Think of a turnstile that accepts coins. A person walks up to a paid resource; instead of "access denied" or "free for all", they get a clear message: "this costs 10 cents — pay and you're in." They pay, the turnstile opens.
x402 is that turnstile, but for software clients. When an automated visitor requests a page or API endpoint you've chosen to meter, it gets back a short, official "payment required" response that states the exact price. Capable agents understand this, pay, and retry — and only then do they get the content. It uses a part of the web's own rulebook (an HTTP response that has existed for "payment required" for decades) that finally has a real use now that the visitors are programs with budgets.
What it means if you run a website
You connect your site once. From then on, AI crawlers that want your content are quoted a price instead of taking it for free. Real people are never affected — they browse exactly as before. You decide which paths cost money and how much. Traffic that used to be pure cost becomes a stream of small payments, with no manual invoicing and no chasing anyone.
What it means if you sell an API
You pick a route and a price and drop in one small piece of code (an official SDK for your stack — there are nine, covering most languages and frameworks). That route now answers unpaid calls with the price, and serves the result once payment is made. You don't write any payment code yourself; the platform handles the money side. Agents that need your API just pay per call.
You don't pay until it works (test mode)
Every account has a sandbox. In test mode the whole flow — request, price, payment, access — runs end to end without any real money, so you can wire it up and confirm it behaves before a single real cent moves. Switching to live is a setting change, not a rewrite.
Why this matters now
The web is being consumed by software at a scale humans never matched. "Block or give away" isn't a strategy. x402 turns automated demand into something you can price and get paid for — using an open, standard mechanism rather than a proprietary middleman. It's the missing "this costs money" handshake for the agentic web.
Next steps
- Running a site and want to charge AI crawlers: for site owners
- Selling an API to agents: for developers and the SDKs
- Want the protocol-level detail: the technical deep dive
- Ready to try it: create an account