JAVASCRIPT SDKv0.3.38

Use HTTP payment challenges.

Try it first

Inspect an HTTP payment challenge#

You need A supported endpoint and a Base Sepolia test client.

Request the protected resource and inspect its payment challenge.
Check network, recipient and atomic-unit amount before authorizing payment.
Retry the same protected operation using its payment proof.

Check your result The resource is released only after the matching payment is verified.

An advanced Playmos x402-shaped envelope over the transfer settlement core.

Choose this after the basic payment flow#

This service product is server-only: use your sk_test_ key, Base Sepolia and an enabled x402 settlement capability. Public pk_ keys and live/mainnet x402 are refused. Use IAP pay → verify for game purchases. This route is for HTTP services that deliberately integrate Playmos challenges. It is not a claim of interoperability with every stock x402 client or facilitator.

Local shape versus service challenge#

createPaymentRequirement and createX402Challenge build a local 402 response with a PAYMENT-REQUIRED header. They do not register a settleable challenge on the service. Use client.x402.challenge and fulfill, or client.x402.pay which performs that sequence.

Keep units explicit#

The SDK takes amount: '0.10'. The envelope’s maxAmountRequired is atomic USDC: '100000'. Network is key-selected Base Sepolia for test keys. Decode and validate challenge inputs; server-issued terms and fees are authoritative, not edits from the client.

Inspect the settlement result#

The result can remain pending or settling; only settled is terminal success, and failed is failure and the actual transaction hash. A locally constructed 402 body is not evidence that money moved. Persist a stable requirement ID before creating the challenge and retain the returned requirement to reconcile interrupted fulfillment with the same terms. A new ID creates a new operation.

If it did not work#

Do not translate display decimals directly into atomic units or assume compatibility with every x402 implementation.

Try one variation Change the expected amount in an isolated verification test. A mismatched proof must not release the resource.

Continue with the next guide →

import { Playmos } from '@playmos/sdk';
import { createPaymentRequirement, createX402Challenge } from '@playmos/sdk';
export function localHttpChallenge(payTo: `0x${string}`) {
const requirement = createPaymentRequirement({
payTo, amount: '0.10', network: 'base-sepolia',
});
return createX402Challenge(requirement, { feeBps: 0 });
// Response shape only: 402, PAYMENT-REQUIRED, atomic maxAmountRequired.
}
export async function payHttpRequirement(
client: Playmos, payTo: `0x${string}`, savedRequirementId: string,
) {
// The SDK mints a service challenge, then fulfills it on Playmos rails.
return client.x402.pay({ payTo, amount: '0.10', feeBps: 0, id: savedRequirementId });
// Inspect settled / settling / failed and the actual transaction hash.
}