X402: How Coinbase Gave New Life to a Dead Internet Protocol
In 2019, Marc Andreessen, early Internet architect and creator of Netscape, called the absence of native payments on the internet an "original sin."Netscape originally tried to build payments into the browser, yet it failed. By his account, the few networks that controlled access to consumers' money had no reason to help build a system designed to bypass them.
The failure to make Internet-native payments a reality in the 1990s created the digital economy we know today: advertising, subscriptions, and typing your card number into a form.
But the engineers that wrote HTTP, the rulebook every website follows to send and receive information, left the backdoor unlocked. They set aside a status code for a payment system that did not exist yet and called it 402, payment required. It shipped with no instructions, because nobody knew what internet-native payment would look like in 1997.
Thirty years later, x402 is trying to absolve that original sin. It is a project to make internet-native payments viable by combining cryptocurrency with a decades-old digital artifact to prepare the web for a new type of commerce: agentic payments.
What is x402?
HTTP 402 first appeared in RFC 2068, the January 1997 specification for HTTP/1.1, the foundational web protocol. 402 was designed as a placeholder for pages that are blocked behind digital cash and micropayment systems – neither of which existed in 1997. The current specification, RFC 9110 from 2022, defines code 402 in one line: reserved for future use.
x402 is a project to give code 402 a purpose, introduced in 2025 by Coinbase and now maintained through the x402 Foundation alongside Cloudflare. x402 is not a payment company, a wallet, or a checkout button. It is a structured format for a server to verify and settle a transaction inside a 402 response. Both the quoted price and the payment travel in ordinary HTTP headers between the client and server without a checkout page, credit card, or processor in the middle.
The original issue for code 402's viability was finding a suitable alternative to credit and debit cards as a payment instrument. The "digital cash" the 1997 specification held a seat for eventually arrived, yet it showed up under a different name: cryptocurrency.
x402 runs on cryptocurrency by design, and for a specific reason. If a payment has to fit inside a single web request, it has to be something software can send on its own, settle in about the time a page loads, and cost a small fraction of the amount being paid. Cryptocurrency checks all three boxes; no other payment method checks more than two.
The fractional processing fees are especially important. Right now, x402 is mainly used for small purchases, a few cents to a couple dollars. A five-cent charge makes no sense on a credit card; the fixed processing fee alone is six times the sale. Cards also authorize in seconds but take days to settle and stay reversible for months afterward. A stablecoin transfer on a layer-two network costs fractions of a cent and reaches final settlement in roughly two seconds.
Here a simple breakdown of how x402 works:
- A client requests a resource from a server.
- The server answers 402 and describes the payment it wants: amount, accepted asset, network, recipient.
- The client signs a payment payload and repeats the request with that payload in a header.
- The server verifies the payment through a facilitator that handles settlement, then returns the resource.
The simplicity is part of the appeal. Four steps, no accounts, and no cards. It’s a departure from how nearly everything online gets paid for today.
Why x402 matters for AI agents
Artificial intelligence works best when there is a machine-readable structure in place to guide its actions. If agents were given total freedom to spend money online and expected to work out how every website's checkout portal functioned ad hoc, it would be pandemonium.
An agent that hits x402, however, gets a structured message naming the price, the asset, and the recipient. Because the response is built on a status code from the HTTP specification rather than any one company's checkout page, every implementation answers the exact same way.
x402 only makes sense because of agentic commerce. It is changing how computers buy things from other computers, not how people buy things online. You will still likely input credit card details and click buy now yourself for that new pair of shoes.
The bet is that a second economy emerges beneath the consumer web, built around AI's need to pay for data as it crawls through API endpoints. Without a way for an agent to pay for access, data providers are left exposed to agents taking everything they need without paying a cent.
Betting on the API economy
Investment in x402 is coming from two directions: AI companies building toward agentic commerce, and financial companies making sure their rails work when it arrives.
x402 is also not the only project in development. The Agentic Commerce Protocol from OpenAI and Stripe standardizes merchant checkout, and Google's AP2 handles authorization, which in this case means cryptographic proof that a user approved what their agent did. They each handle different parts of a transaction, so a single purchase can involve more than one.
Fifteen years ago, tech and media worked out how to profit from the digital economy: advertising and data brokerage. x402 is the infrastructure meant to produce that same moment for the agentic economy by creating the revenue structure around API calls. The open question is how much an x402 API call should cost, which is what developers are still in the process of working out.
Cloudflare launched Pay Per Crawl in 2025, letting publishers charge AI crawlers a set rate per request through 402 responses. However, a year later it changed the model, and shifted pricing toward paying publishers when their content appears in an AI-generated answer instead.
Charging per fetch priced the wrong moment: AI may pull an enormous number of pages and use just a few of them to produce an answer, so a page that shaped an answer earned the same few cents as one the model discarded. The thing worth charging for was appearance in an answer, not retrieval. This sort of pricing experimentation is reminiscent of the early influencer economy, when advertising became priced per mention, click, or conversion.
Something is clearly working for x402. Chainalysis counted more than 100 million x402 transactions on Base through early 2026, wallet retention is climbing, and the money now moves in payments above a dollar rather than fractions of a cent. Although volume numbers may be inflated from an uptick in minting PING memecoins last year, the general trends for the protocol look promising.
Big players are getting involved, too. Amazon now offers managed x402 payments for agents on Bedrock, and Visa and Mastercard are now part of the x402 Foundation.
Slash is building for whatever comes next. Our AI agent, Twin, already executes and orchestrates payments with supported providers, and we support USDC and USDT natively.⁴ The two things any version of agentic payments requires — software that can transact and stablecoin settlement — are already part of how our users move money.
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