What Is x402? HTTP Payments For AI Agents Explained
Dominic Tarn
Head Writer - ReVerb
11.10.2026
When the web’s builders wrote HTTP in the 1990s, they reserved a status code for a future that never arrived: 402 Payment Required. Nearly thirty years later, x402 finally puts it to work. It is an open protocol that lets software, and especially AI agents, pay for a web resource inside a normal HTTP request, usually with a stablecoin, without accounts, subscriptions or card details. This guide explains what x402 is, how it works, who backs it and when it makes sense in 2027.
What Is x402?
x402 is an open standard for internet-native payments. A server can answer a request with HTTP 402 and a price. The client, often an AI agent, attaches a payment and repeats the request, and the server returns the content once payment is verified. Settlement typically happens in USDC on a fast, low-cost blockchain in a couple of seconds.
The aim is to make paying for an API call, a dataset, an article or a few seconds of compute as simple as loading a page, at prices as small as a fraction of a cent, which card payments cannot handle economically.
How x402 Works
1. Request. An agent asks a server for a resource, such as an API endpoint.
2. 402 response. The server replies with 402 Payment Required and machine-readable payment terms: price, accepted asset, network and where to pay.
3. Payment. The agent signs a stablecoin payment authorization from its wallet and sends the request again with the payment attached in a header.
4. Verification and settlement. The server, often through a facilitator service, verifies the payment and settles it on-chain.
5. Delivery. The server returns the resource along with a receipt.
Because everything happens inside HTTP, x402 works with existing web servers, APIs and agent frameworks. Facilitators handle blockchain details so sellers do not need to run crypto infrastructure themselves.
Who Is Behind x402
Coinbase introduced x402 in May 2025. In 2026 it contributed the protocol to the x402 Foundation at the Linux Foundation, which became fully operational in July with dozens of member organizations, including Coinbase, Cloudflare, Stripe, Google, AWS, Visa, Mastercard, American Express and the Solana Foundation.
Support has spread across the stack. Stripe added x402 for USDC payments on Base in February 2026, Cloudflare supports it in its Agents SDK and at the network edge, Google’s Agent Payments Protocol includes an x402 extension for agent-to-agent payments, and Coinbase lets its business customers accept USDC from agents through x402. Payments run on several networks, including Base and Solana.
How Much Is x402 Used?
Coinbase reported about 165 million transactions, roughly $50 million in cumulative volume and around 69,000 active agents by late April 2026. Those numbers are real but need context: much of the volume is small, experimental or automated test traffic rather than mature commerce. The signal that matters more is that the major payment companies and card networks have joined its governance.
What x402 Is Good For
Paid APIs and data: charge per call instead of selling subscriptions and API keys.
Agent tools: let agents buy search results, scraping, compute or premium data on demand.
Content: charge AI crawlers and agents for articles or media per access.
Agent-to-agent services: let one agent pay another for a task.
x402 vs Other Agent Payment Approaches
Approach
Best For
How It Pays
x402
Machine-to-machine micropayments
Stablecoins inside an HTTP request
Machine Payments Protocol (Stripe and Tempo)
Ongoing machine usage
HTTP 402 with session-based billing
Agentic Commerce Protocol (Stripe and OpenAI)
Agents checking out with merchants
Scoped tokens on existing payment methods
Google AP2
Proving what a user approved
Signed mandates across cards, banks and crypto
Visa and Mastercard agent programs
Consumer purchases on cards
Agent-specific card tokens
These are complementary. An agent might use AP2 to prove it is allowed to spend, card tokens to buy a product and x402 to pay for the data it used to choose. Our list of agent payment platforms and protocols compares them.
Limits And Risks
Finality: stablecoin payments settle quickly and cannot be charged back, so refunds are up to the seller.
Wallet security: an agent’s wallet is a target; keep balances small and spending limits tight.
Manipulation: an agent tricked by prompt injection could pay the wrong party; see our guide on what prompt injection is.
Regulation and accounting: stablecoin payments raise tax, reporting and compliance questions that vary by country.
How To Get Started
To accept x402: add x402 middleware to your API or use a platform that supports it, set prices per request and choose a facilitator to handle verification and settlement.
To pay with x402: give your agent a wallet with a small USDC balance and a spending cap, and use an agent framework or SDK with x402 support.
No. x402 is a protocol, not a cryptocurrency. Payments are usually made in existing stablecoins such as USDC.
Is x402 Only For Crypto Companies?
No. The point is to make crypto invisible. Sellers can use facilitators and payment providers that handle the blockchain side.
Do Humans Use x402?
It can work for people, for example paying a few cents to read an article, but it was designed with agents and software in mind.
Who Controls x402?
The x402 Foundation under the Linux Foundation, with vendor-neutral governance.
Conclusion
x402 turns the long-dormant HTTP 402 status code into a working payment layer for the agent era: request, get a price, pay, receive. It is backed by Coinbase, the Linux Foundation and most of the payments industry, and it is the leading option for small, frequent machine-to-machine payments. For API, data and content businesses, it is worth testing now; for consumer shopping, it works alongside card-based agent payments rather than replacing them.
