x402

x402 is an open payment standard that activates HTTP 402 Payment Required for practical use. It lets agents and applications charge for API access with a standard HTTP flow:

1. Client requests a paid resource
2. Server responds with 402 Payment Required
3. Client signs a payment payload
4. Client retries with payment attached
5. A facilitator verifies and settles on-chain

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When to use x402

Use x402 when you want:

• the simplest pay-per-request integration path
• a public facilitator on Abstract
• a clean split between client and server middleware

Use MPP instead when you want HTTP-native charge and session payment modes in one protocol, especially for repeated micro-payments.

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Abstract facilitator

Abstract runs a public x402 facilitator that any developer can use:

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Supported token

The facilitator works with any ERC-3009-capable token on Abstract. USDC is the recommended token:

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x402 vs MPP

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