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What is x402

Payment terms in one HTTP response.

x402 is an open standard that lets a website describe a payment using HTTP 402, "Payment Required." A compatible client can read the challenge, ask a wallet to authorize the stated amount and recipient, then retry the request after settlement.

See how it settles Read the protocol docs
Open HTTP payment standard Explicit wallet approval Direct merchant settlement
x402 request sequence A protected route answers with payment terms; the client authorizes them and retries the request to receive the paid response. PAID REQUEST SEQUENCE GET 01 Protected route 402 02 Payment terms SIGN 03 Payment proof 200 04 Paid response The client reads the terms, authorizes payment, and retries the request. x402 request sequence A protected route answers with payment terms; the client authorizes them and retries the request to receive the paid response. PAID REQUEST SEQUENCE GET Protected route 01 402 Payment terms 02 SIGN Payment proof 03 200 Paid response 04 The client reads the terms, authorizes payment, and retries.
x402 request sequence A protected route answers with payment terms; the client authorizes them and retries the request to receive the paid response.
Read the official x402 source →

The payment requirement travels in HTTP. The wallet still controls approval.

The open standards x402 is built on

The buyer's view

How a payment feels

  1. 01

    You reach a paid page

    You click "buy" — or an app you use does. Instead of a card form, the server replies with a small machine-readable note: "this costs $29 in USDC."

  2. 02

    Your wallet signs

    Your crypto wallet reads that note and asks you to approve one payment. You see the exact amount and the recipient before you confirm. Nothing is charged until you do.

  3. 03

    The selected rail settles

    The selected facilitator and network settle the authorized USDC to the merchant wallet. LinkSell does not create a merchant balance.

Under the hood

The same payment, drawn as a diagram

The same payment, showing every role it passes through: the buyer's wallet, the terms, the facilitator, the network, and the merchant's wallet. Settlement time depends on the live network and facilitator.

A hosted x402 payment

The buyer reviews terms, authorizes payment, and receives the result after the selected rail settles.

A hosted x402 payment The buyer reviews terms, authorizes payment, and receives the result after the selected rail settles. VISIBLE TERMS → AUTHORIZATION → SETTLEMENT Terms Shown 01 Wallet Approves 02 Live rail Settles 03 Merchant Receives 04 Record Updates 05 A hosted x402 payment The buyer reviews terms, authorizes payment, and receives the result after the selected rail settles. TERMS → AUTHORIZATION → SETTLEMENT Terms Shown 01 Wallet Approves 02 Live rail Settles 03 Merchant Receives 04 Record Updates 05
Terms before authorization. The wallet shows the terms before approval.
What a buyer needs before paying A compatible wallet, a live supported network, and the requested asset must all be present before the checkout can complete. Buyer prerequisites Wallet Signs the terms Live network Supported rail USDC asset Requested amount Costs shown Reviewed first Ready to pay Current facts Rail state LIVE or evaluating What a buyer needs before paying A compatible wallet, a live supported network, and the requested asset must all be present before the checkout can complete. Buyer prerequisites Wallet Signs the terms Live network Supported rail USDC asset Requested amount Costs shown Reviewed first Ready to pay Current facts Rail state LIVE or evaluating
What a buyer needs before paying A compatible wallet, a live supported network, and the requested asset must all be present before the checkout can complete.

New to crypto? Read this first

You need a compatible wallet and supported USDC.

USDC is designed to maintain parity with the US dollar and Circle describes it as redeemable 1:1 under its terms. That design is not a LinkSell guarantee: market price, issuer, wallet, facilitator, and network risks still exist. Read Circle's USDC information.

The wallet must support the live network and authorization requested by the checkout. Network, facilitator, wallet, and conversion costs can vary; x402 itself publishes zero protocol fees. Check the amount, recipient, network, and any displayed costs before signing.

The merchant's view

Why merchants choose it

  • Zero x402 protocol fees; LinkSell charges 0% commission per sale
  • Funds settle to the merchant wallet on the selected live rail
  • Non-custodial — no processor holds the money
  • No card chargeback after settlement; seller-issued refunds remain possible
  • Works for people and for AI agents that pay autonomously
  • Open standard — not locked to one vendor

Hosted, never custodial

LinkSell hosts x402 checkout so merchants don't have to.

The technical detail — the 402 challenge envelope, the signed payment header, and a sample client you can run — lives in the developer docs.

Request access Read the docs