What Is x402? The HTTP 402 Stablecoin Payment Protocol

x402 is an open payment protocol that uses the long-dormant HTTP 402 "Payment Required" status code to let websites, APIs and AI agents charge and pay for things in a single web request, usually in stablecoins such as USDC. A server answers a request with a 402 and a price, the client signs a payment and retries, and the server returns the content once the payment settles onchain. No account, subscription or API key is needed.

Coinbase created x402 and launched it in May 2025. Since 2026 it has been governed by the x402 Foundation at the Linux Foundation, whose members include Cloudflare, Google, Visa, Mastercard, Stripe and Circle.

How x402 works, step by step

HTTP status codes are the three-digit replies a web server sends with every response: 200 means OK, 404 means not found. Code 402 has existed for decades, but the current HTTP standard, RFC 9110, still says only that it "is reserved for future use". x402 gives it a concrete job.

The x402 documentation describes the flow like this:

Request. A client (a browser, an app or an AI agent) asks a server for a paid resource, such as an API endpoint or an article.
402 response. The server replies with status 402 and a PAYMENT-REQUIRED header. It lists the accepted options: the payment scheme, the network, the token, the amount and the address to pay.
Signed payment. The client picks one option and signs a payment payload with its wallet. On EVM chains this is usually an off-chain signature that authorises a token transfer, so the buyer does not have to send a transaction itself.
Retry. The client sends the same request again with the signed payload in a PAYMENT-SIGNATURE header.
Verify and settle. The server checks the payload, either itself or by calling a facilitator's /verify endpoint, then settles the payment onchain, directly or through the facilitator's /settle endpoint.
Delivery. The server returns 200 OK with the content and a PAYMENT-RESPONSE header that confirms the settlement.

Those three header names belong to version 2 of the protocol. All three carry Base64-encoded JSON, according to the HTTP 402 page of the docs:

Header	Direction	What it carries
PAYMENT-REQUIRED	Server to client	Price, accepted networks, token and destination address
PAYMENT-SIGNATURE	Client to server	The buyer's signed payment payload
PAYMENT-RESPONSE	Server to client	The settlement result, successful or failed

The protocol defines several payment schemes. Exact charges a fixed price per request. Upto lets the buyer authorise a maximum and pay only for what is used, which suits metered services such as AI model output. Batch-settlement has the buyer deposit into an escrow once and then sign off-chain vouchers per request, which the seller redeems in batches. Auth-capture holds funds in escrow until the resource is served, so a payment can still be voided or refunded.

What a facilitator does

A facilitator is an optional service that verifies payment payloads and submits them to the blockchain for the seller. It lets an API provider accept onchain payments without running nodes or writing its own verification code.

The docs stress that a facilitator "does not hold funds or act as a custodian". Every payload is signed by the buyer, so a facilitator that tampered with a payment would fail the signature check and could not settle it. Anyone can run one. The facilitator list includes services from Coinbase, Fireblocks, Polygon and Celo, plus a public facilitator for Stellar, and a seller can also self-host or settle directly.

Coinbase's own CDP Facilitator was free for the first 1,000 onchain transactions a month and $0.001 per transaction after that, as of 12 October 2026. It runs OFAC and Know Your Transaction (KYT) checks to decline payments involving sanctioned or high-risk addresses. That matters because x402 has no compliance layer of its own: screening, if any, happens at the facilitator or the seller. Our guide to the OFAC sanctions list explains what that screening checks.

Which networks and tokens x402 supports

x402 identifies networks with CAIP-2 chain IDs, so it is not tied to one blockchain. As of 12 October 2026, the networks and token support page lists:

Any EVM chain, with any ERC-20 token, through EIP-3009 transferWithAuthorization (used by USDC) or Uniswap's Permit2 as a fallback. Default stablecoins are preconfigured for Base, Ethereum, Arbitrum, Polygon, Avalanche, Celo, Sei, Monad, Stable, XDC and Circle's Arc, among others.
Non-EVM networks including TON, Algorand, Stellar, Aptos, Hedera, NEAR, XRPL, Cardano, Concordium and Keeta.

Base is the original home of x402 and still its main production network. Most quick-start examples default to USDC on Base, and USDC is the default dollar asset on most of the listed chains. Other stablecoins work where the chain supports them: USDT0 on Stable, USDT on TON, RLUSD on XRPL. Our post on stablecoin-focused chains covers Arc and the other payment chains in that list.

Two caveats. First, "supported by the protocol" is not the same as "has a production facilitator". The docs separate the two, and a seller has to check that a working settlement path exists for the chain they want. Second, x402 does not move fiat. The x402 FAQ says it does not natively support card deposits or off-ramps, though facilitators or third-party gateways can add them.

A short history: from Coinbase project to Linux Foundation standard

6 May 2025: Coinbase Developer Platform introduced x402 as "a new standard for internet-native payments", launching with AWS, Anthropic, Circle and NEAR as collaborators.
16 September 2025: Google announced its Agent Payments Protocol (AP2) and, with Coinbase and others, an A2A x402 extension for agent-based crypto payments.
23 September 2025: Cloudflare announced it was partnering with Coinbase to create the x402 Foundation. It added x402 to its Agents SDK and MCP integrations and proposed a deferred payment scheme for its pay-per-crawl beta.
11 December 2025: The Block reported the rollout of x402 V2, which introduced the standardised headers and network IDs described above.
2 April 2026: The Linux Foundation announced the x402 Foundation and Coinbase's contribution of the protocol. Organisations expressing initial support included Adyen, AWS, American Express, Circle, Cloudflare, Google, Mastercard, Microsoft, Shopify, Stripe and Visa.
14 July 2026: The foundation became fully operational, with 40 member organisations. Coinbase's contribution was complete.

The code now lives in the x402-foundation GitHub repository under the Apache-2.0 licence, with reference SDKs in TypeScript, Python and Go. The FAQ is explicit that x402 is not a Coinbase product and that you don't need any Coinbase service to use it.

How much is x402 actually used?

The x402.org homepage showed, for the last 30 days as of 12 October 2026, about 75.41 million transactions, $24.24 million in volume, 94,060 buyers and 22,000 sellers across all networks. That works out to an average payment of roughly $0.32, which fits the micropayment pitch.

Treat raw counts with care. Analytics firm Artemis classifies x402 transactions as "real" or "gamed", and a February 2026 Four Pillars analysis of its data found that gamed transactions averaged 63.94% of the total between 9 November 2025 and 7 February 2026, peaking at 90.21% on one day. The same analysis found that 30 new wallets generated about 1.93 million of 2.1 million x402 transactions on Polygon in late January 2026 before stopping almost at once. Cheap transactions are easy to farm. An adjusted estimate by Sheffield, a Visa executive, reported by The Defiant on 16 July 2026, put x402 volume at about $19 million once wash and test activity was stripped out, with roughly 4,000 wallets driving about 90% of the adjusted spending.

So x402 is live and growing, but genuine agent-to-API commerce is still a small, concentrated market. Headline transaction counts overstate it.

x402, stablecoin payments and agentic commerce

x402 is a narrow piece of a bigger shift. Stablecoins give it a dollar-denominated asset that settles in seconds on low-fee chains, which card networks cannot do economically for a $0.01 API call. Our explainer on how stablecoins work covers the basics, and stablecoin payments in 2026 covers the wider market.

The main use cases sellers are testing:

Pay-per-call APIs for data, search, inference or compute, priced per request instead of per monthly plan.
AI agents buying tools mid-task. The docs include a guide to using x402 with an MCP server, so a model can pay for a paid tool without a human entering card details.
Paywalled content and crawling, where a publisher charges per page or per crawl, as in Cloudflare's pay-per-crawl proposal.

x402 is not the only standard. Google's AP2 is a broader agent-payments framework that also covers cards and bank transfers, and offers an x402 extension for crypto payments. Stripe and Paradigm launched the Tempo chain in March 2026 alongside a separate Machine Payments Protocol (MPP); see our Tempo explainer. Stripe is also a member of the x402 Foundation, so these standards may end up working alongside each other rather than competing outright.

Risks and limits

Payments are final. The exact scheme is a push payment and cannot be reversed. Refunds depend on the seller sending funds back, unless an escrow-style scheme is used. There are no card-style chargebacks.
Agent wallets are hot wallets. An agent that pays on its own needs a key that can sign without a human. If that key leaks or the agent is manipulated, for example by prompt injection, it can spend whatever the wallet holds. Keep agent wallets small and use spending limits.
Stablecoin risk. Payments are only as sound as the token. Issuer, reserve and depeg risks still apply; see stablecoin depegs explained.
Compliance sits outside the protocol. x402 does not identify buyers. Sellers with sanctions or AML obligations need a facilitator that screens, or their own controls. Stablecoin rules such as the US GENIUS Act govern the issuer, not every API that accepts its token.

Where JewelSwap fits

JewelSwap does not use x402. Its DeFi apps run on MultiversX, Sui and Radix, none of which appear on the x402 network list as of 12 October 2026. If you hold stablecoins on Sui, our guide to DeFi on Sui covers the lending protocols and DEXs that use them there.

Frequently asked questions

What is x402 in simple terms?

x402 is an open protocol that lets a website or API ask for payment using the HTTP 402 "Payment Required" status code. The client pays in a stablecoin such as USDC by signing a payment and retrying the request, and receives the content once the payment settles onchain. No account or API key is needed.

Who created x402 and who runs it now?

Coinbase created x402 and launched it in May 2025. Coinbase contributed the protocol to the x402 Foundation at the Linux Foundation, announced on 2 April 2026 and fully operational from 14 July 2026 with 40 members, including Cloudflare, Google, Visa, Mastercard, Stripe and Circle.

Does x402 only work with USDC on Base?

No. Base and USDC are the most common setup, but x402 supports any EVM chain and any ERC-20 token, plus non-EVM networks such as Stellar, Aptos, Hedera, NEAR, XRPL, TON and Cardano. A seller also needs a facilitator or settlement path that supports the chosen network.

Does x402 charge fees?

The protocol itself has no fees. Buyers and sellers pay normal network fees, and some facilitators charge for settlement. Coinbase's CDP Facilitator, for example, was free for 1,000 onchain transactions a month and then $0.001 per transaction as of 12 October 2026.

Is x402 safe for AI agents to use?

The protocol is designed so facilitators cannot alter a buyer's signed payment, but payments are final and an agent's wallet is effectively a hot wallet. If its key leaks or the agent is tricked, funds can be spent. Keep balances small, set spending limits and check what each endpoint charges.

Does JewelSwap support x402?

No. JewelSwap runs on MultiversX, Sui and Radix and does not integrate x402. None of those three networks appear on the x402 network list as of 12 October 2026.

Keep reading

This article is educational and is not financial or legal advice. Figures are as of 12 October 2026 unless dated otherwise. Sources: x402 Foundation documentation, x402.org, Coinbase Developer Platform, the Linux Foundation, Cloudflare, Google Cloud, The Block, Four Pillars and The Defiant.

Viktor Vostrikov

Co-Founder

About the author.

Co-Founder at JewelSwap & Chief Strategy Officer at iDenfy. Viktor brings his successful track record of superb development & project management.