Question 1

What is x402?

Accepted Answer

x402 is an open HTTP payment protocol that reactivates the long-dormant 'HTTP 402 Payment Required' status code. Instead of forcing every API to build its own billing, subscription, and auth stack, x402 lets a server reply to any request with a 402 response that includes machine-readable payment requirements. The client - a human browser extension, a script, or an autonomous AI agent - reads those requirements, pays on-chain with USDC or another stablecoin, and retries the request with a proof-of-payment header. x402 was introduced and open-sourced by Coinbase in May 2025, with governance transitioning to the Linux Foundation-hosted x402 Foundation in April 2026.

Question 2

How does x402 work?

Accepted Answer

The x402 flow has five steps. (1) The client makes a normal HTTP request to a paid endpoint. (2) The server replies with HTTP 402 and a PAYMENT-REQUIRED header describing the chain, token, amount, and recipient. (3) The client signs a payment payload (no on-chain transaction yet) and retries the request with a PAYMENT-SIGNATURE header. (4) The server forwards the signed payload to a stateless facilitator, which verifies the signature and then settles the payment on-chain. (5) Once settlement confirms, the server returns the paid response with a PAYMENT-RESPONSE header. The entire round-trip can complete in seconds on a fast chain like Base or Solana.

Question 3

What is a facilitator in x402?

Accepted Answer

A facilitator is a stateless service that sits between resource servers and the blockchain. It verifies payment proofs, optionally broadcasts transactions, and returns a simple 'paid/not-paid' verdict. This keeps resource servers simple: they never hold private keys, never run a chain node, and never touch settlement logic. Anyone can run a facilitator, and servers can choose whichever facilitator they trust.

Question 4

x402 vs Stripe - what's the difference?

Accepted Answer

Stripe is a centralised payment processor that requires both buyer and seller to hold Stripe accounts, go through KYC, and settle in fiat through card networks. x402 is a protocol, not a company: there are no accounts, no card numbers, and no platform fees beyond the underlying chain's gas. Stripe is optimised for humans paying businesses; x402 is optimised for software - including AI agents - paying any HTTPS endpoint in the world. They are not direct competitors and many builders will use both.

Question 5

x402 vs L402 - what's the difference?

Accepted Answer

L402 is an earlier payment protocol from Lightning Labs that uses Bitcoin's Lightning Network for settlement and LSAT (Lightning Service Authentication Tokens) for auth. x402 is chain-agnostic but in practice settles on Base, Solana, and other low-fee EVM or SVM chains using USDC. L402 has the brand recognition of Bitcoin and the atomic guarantees of Lightning; x402 has stablecoin pricing, broader chain support, and a simpler header-only integration. Both protocols can coexist - a server can advertise multiple payment options in a single 402 response.

Question 6

Which chains support x402?

Accepted Answer

As of April 2026 the chains with production x402 facilitator support via Coinbase's reference facilitator are Base, Solana, Polygon, Arbitrum, and World Chain. Additional chains including Avalanche, Sei, XDC, and SKALE have community or ecosystem facilitator implementations at varying maturity (production or beta). Base and Solana were the launch chains, chosen for their low gas fees and native USDC liquidity. The x402 spec is chain-agnostic and uses CAIP identifiers, so any chain with a facilitator implementation can be added. Ethereum mainnet works but is typically too expensive for true micropayments. Expect the list to keep growing.

Question 7

Which stablecoins can I use with x402?

Accepted Answer

As of April 2026, USDC is the default and most widely supported settlement asset. USDT is supported by some facilitators such as Utexo on Bitcoin Lightning. Additional stablecoins may be supported by individual community facilitators. A resource server declares which assets it accepts in the 402 response, so the client always knows the exact token before paying.

Question 8

How do I integrate x402 into my API?

Accepted Answer

There are three typical integration patterns. (1) Use the official x402 server SDK in Node, Python, or Go - you wrap a handler and declare a price per route. (2) Put a gateway or reverse proxy in front of an existing API - services like AgentPay and the x402 gateway handle enforcement without code changes. (3) Implement the protocol directly - return 402, include the payment-requirements header, verify the payment-proof header against a facilitator on retry. Option (1) is the fastest for most teams.

Question 9

Do I need a wallet to use x402?

Accepted Answer

As a consumer client you need some way to sign payments - typically a browser extension wallet, an embedded wallet in an agent runtime, or a server-side signer funded from treasury. As a resource server operator you do NOT need a wallet: facilitators handle signing and on-chain interaction, and payments land directly in whatever address you specify.

Question 10

Who created x402?

Accepted Answer

x402 was designed and open-sourced by Coinbase in May 2025, with the first public spec and reference implementation published under coinbase/x402 on GitHub. Governance transitioned to the Linux Foundation-hosted x402 Foundation on 2 April 2026, launching with 22 founding participants: Adyen, Amazon Web Services, American Express, Ampersend.ai, Base, Circle, Cloudflare, Coinbase, Fiserv Merchant Solutions, Google, KakaoPay, Mastercard, Merit Systems, Microsoft, Polygon Labs, PPRO, Shopify, Sierra, Solana Foundation, Stripe, thirdweb, and Visa.

Question 11

Is x402 open source?

Accepted Answer

Yes. The protocol specification, reference facilitator, and client and server SDKs are open-source under permissive licences. Anyone can run a facilitator, fork the spec, or contribute pull requests.

Question 12

Is x402 safe?

Accepted Answer

Like any on-chain protocol, the security model depends on the chain and the facilitator. Payments are final once settled - there is no chargeback mechanism. Nonces and expiries prevent replay attacks. As a client you are only ever risking the exact amount demanded by the 402 response, which for most APIs is a fraction of a cent. For larger payments, use clients that surface the amount and recipient before signing.

Question 13

What is agentic commerce?

Accepted Answer

Agentic commerce is any transaction where one or both counterparties are autonomous software agents rather than humans. The rise of AI agents that can research, decide, and act has created demand for a payment rail that supports zero-friction, zero-login, machine-initiated payments - which is exactly the problem x402 solves.

Question 14

Can AI agents use x402 autonomously?

Accepted Answer

Yes - this is one of x402's primary design goals. An agent equipped with a signing key and a USDC balance can detect a 402 response, evaluate whether the price is acceptable, pay, and retry the request without any human involvement. Agent frameworks such as LangChain have community x402 integrations available; x402 can also layer on top of Anthropic's Model Context Protocol (MCP) when an MCP tool gates calls behind payment. Official runtime-level integrations from OpenAI and Anthropic have not been announced.

Question 15

What does x402 cost to use?

Accepted Answer

The protocol itself has no fees. The only costs are the amount demanded by the resource server (set per endpoint) and the underlying chain's gas. On Base and Solana, gas for a USDC transfer is typically well under one cent, which is what makes true micropayments practical.

Question 16

Can I refund an x402 payment?

Accepted Answer

Refunds are out-of-band: the protocol has no chargeback, so refunds are implemented as a regular on-chain transfer from the server back to the client. Receipt metadata in the paid response typically carries the data a server would need to honour a refund.

Question 17

Is x402 a blockchain?

Accepted Answer

No. x402 is an HTTP protocol that USES blockchains for settlement. It has no native token, no ledger, and no consensus layer of its own. It is purely a set of headers and conventions for negotiating payment over standard HTTPS.

Question 18

Does x402 have a token?

Accepted Answer

There is no official x402 token. The protocol settles in existing stablecoins (primarily USDC). Any token claiming to be 'the x402 token' should be treated with extreme scepticism.

Question 19

Where can I follow x402 news?

Accepted Answer

x402 Daily publishes a daily briefing at x402daily.xyz and posts the top stories to @x402daily on X. The official Coinbase x402 blog and the coinbase/x402 GitHub repository are the canonical sources for spec changes and releases.

Question 20

How do I try x402 today?

Accepted Answer

The fastest path is to clone the coinbase/x402 repository, spin up the reference facilitator on Base Sepolia (testnet), and run the example server. On the client side, x402-axios wraps axios so any outbound HTTP call can transparently pay for 402 responses. Most teams go from zero to a paid endpoint in an afternoon.

Question 21

How much volume has x402 processed?

Accepted Answer

As of late April 2026, two complementary public datasets are circulating. Coinbase's Jesse Pollak told CoinDesk on 25 April 2026 that roughly $48 million had settled through x402 on Base, driven by 480,000+ transacting agents at an average payment of $0.31. Separately, Insignia Business Review (24 April 2026), drawing on Agent.market data, cites approximately 69,000 active agents processing 165 million transactions for around $50 million in cumulative x402 volume. The two figures aren't directly comparable - Pollak's count is Base-only, the Insignia figure spans the wider x402 ecosystem - but both confirm true micropayment scale. x402 Daily tracks the running totals on the homepage and in the daily archive.

Question 22

Is x402 production-ready?

Accepted Answer

Yes - x402 moved decisively from experiment to infrastructure in early 2026. The Linux Foundation took over governance of the x402 Foundation on 2 April 2026 with 22 founding participants including Google, AWS, Microsoft, Visa, Mastercard, Stripe, Cloudflare, Circle, and Coinbase. AWS shipped a reference architecture wiring x402 into Bedrock AgentCore on 25 April 2026, and independent VC analysis (Insignia Business Review, April 2026) describes x402 as having 'transitioned from early-stage experiments into production infrastructure'. Public reporting points to 480,000+ transacting agents on Base and tens of thousands of active agents across the wider ecosystem.

Question 23

How fast is x402 settlement?

Accepted Answer

Settlement latency depends entirely on the underlying chain. On Base (a Coinbase-backed Ethereum L2), USDC settlement typically confirms in 1-3 seconds. On Solana, settlement is sub-second. On Utexo's Bitcoin-native execution layer (USDT settlement), the operator claims roughly 50ms finality. End-to-end an x402 round-trip - 402 response, signed payload, facilitator verification, settlement, paid response - usually completes inside 2-5 seconds on production chains. Polygon, Arbitrum, and World Chain fall in a similar range.

Question 24

What companies use x402?

Accepted Answer

Founding x402 Foundation participants (April 2026) include Coinbase, Cloudflare, Stripe, Google, Microsoft, AWS, American Express, Visa, Mastercard, Adyen, Shopify, Circle, Polygon Labs, Solana Foundation, Sierra, KakaoPay, PPRO, Fiserv Merchant Solutions, Merit Systems, thirdweb, Ampersend.ai, and Base. Public production deployments include AWS Bedrock AgentCore, Coinbase Agent.market, Cloudflare's pay-per-crawl, Bankr x402 Cloud, AEON on BNB Chain, Utexo (USDT settlement), Zerion API, AgentMail, and Venice Skills. Hundreds of indie builders run x402 endpoints via the public catalog.

Question 25

What is the cheapest chain for x402?

Accepted Answer

Solana is generally the cheapest production chain for x402, with USDC transfer fees consistently in the fractions-of-a-cent range thanks to its high-throughput design and lamport-denominated fees. Base (an Ethereum L2 built by Coinbase) is similarly low-cost, typically under one cent for a USDC transfer. Polygon and Arbitrum sit slightly higher but remain practical for micropayments. Ethereum mainnet is technically supported but is almost never used for x402 because gas fees usually exceed the payment amount. For sub-cent micropayments, Solana and Base are the standard choices.

x402 FAQ