Today, PayAI is adding Arbitrum to the list of networks supported by our x402 facilitator.

Any agent, app, or API integrated with PayAI can now accept and pay for resources on Arbitrum using the same x402 flow that already runs across Solana, Base, Polygon, Avalanche, Sei, SKALE, and X Layer. No new SDKs. No new endpoints. Just add arbitrum to your accepts array and you're live.

This is a meaningful expansion. Arbitrum is the largest L2 on Ethereum and a major stablecoin venue in its own right — the chain holds roughly $3.87 billion in stablecoins, with USDC alone making up $2.34 billion of that float (DefiLlama). For an x402 facilitator, that's exactly the kind of liquidity profile that matters: deep, USDC-heavy, and concentrated on a chain that EVM-native teams already build on. Bringing x402 to Arbitrum closes the gap between agentic payments and the Ethereum-aligned builders who want internet-native payments on the L2 their stack already runs on.

PayAI is the largest x402 facilitator on Solana and a top facilitator across the broader x402 ecosystem. Adding Arbitrum is the next step in becoming the default multi-network facilitator for the agentic web — Solana for raw throughput, Base for Coinbase distribution, Arbitrum for EVM ecosystem reach, all from one integration.

What ships today

Arbitrum is now a fully supported network on the PayAI facilitator. Concretely, that means:

  • USDC settlement on Arbitrum One via the standard x402 payment flow, with support for any EIP-3009 token (USDC, PYUSD, USDP, FDUSD, EURC, and others). EIP-3009 is what makes x402 work on EVM: the payer signs an off-chain transferWithAuthorization message, the facilitator submits the transaction, and the merchant gets a fully gasless settlement — no allowances, no approvals, no extra round-trips.
  • Same SDKs, same endpoints. Existing PayAI integrations on Express, Hono, Next.js, FastAPI, Flask, and Go pick up Arbitrum by changing one line of config.
  • Same /verify, /settle, and /supported endpoints — facilitator behavior is identical across networks, so multi-chain merchants don't have to maintain parallel logic.
  • Same facilitator pricing. The first 1,000 settlements per month are free; $0.001 per transaction after that, regardless of network.
  • Testnet support. Build and verify against Arbitrum Sepolia before flipping production traffic over.

The Supported Networks page and the quickstart have been updated. If you've already integrated PayAI on Solana or Base, adding Arbitrum is a config change, not a migration.

Why Arbitrum

The agentic payments thesis only works on rails fast enough and cheap enough to keep up with software-speed transaction volume. Arbitrum qualifies on both counts. The platform is engineered for response times as low as 100ms and throughput up to 6,000 TPS, with a transaction pricing model that meaningfully reduces fee spikes during peak demand. Those are the same characteristics that make x402 viable in the first place — micropayments need finality measured in milliseconds, not minutes, and pricing measured in fractions of a cent, not dollars.

Arbitrum is also already a settlement layer for stablecoins at meaningful scale, and the Arbitrum ecosystem has been actively working through the intersection of blockchain and AI. That's the exact corner of the market x402 was designed for: programmable money meeting autonomous software.

For PayAI, Arbitrum support is part of a deliberate multi-network strategy. x402 is an open standard, and the protocol is designed so that no facilitator and no chain has lock-in. Developers who want to support Solana for raw throughput, Base for Coinbase distribution, and Arbitrum for EVM ecosystem reach can do it from a single integration. We index services across all of them.

"x402 is winning because it's chain-agnostic and facilitator-agnostic. Arbitrum has been one of the most-requested networks from teams shipping on PayAI — they have their stack on EVM, their stablecoins on Arbitrum, and they want their agents paying for things on the same rails. Today they can." — Notorious, founder at PayAI (@notorious_d_e_v)

What this unlocks

A few of the use cases we expect to ship on Arbitrum + x402 first:

  • EVM-native agent payments. Agents holding an Arbitrum wallet with USDC can now discover prices, sign transactions, and access paid resources autonomously — no API keys, no subscriptions, no human in the loop.
  • API monetization for Ethereum builders. APIs deployed in EVM-native dev environments can now monetize per request without leaving the L2 their team and treasury already live on.
  • Cross-chain agent flows. A multi-network agent can pay one service on Solana, another on Arbitrum, and a third on Base — all through PayAI's facilitator, all settled in stablecoins.
  • Onchain payments at human-and-machine speed. Sub-second confirmation and predictable fees mean an Arbitrum-paid API call feels just like a non-paid one.

For builders

If you're already integrated with PayAI: add Arbitrum to the accepts array of your endpoint configuration. On x402 v1, that's arbitrum (mainnet) or arbitrum-sepolia (testnet). On x402 v2 — which uses CAIP-2 chain IDs — it's eip155:42161 (Arbitrum One) or eip155:421614 (Arbitrum Sepolia).1 That's it. Documentation: docs.payai.network.

If you're new to x402 and PayAI: start with the x402 protocol overview, then run the quickstart. You can be accepting USDC on Arbitrum (and seven other networks) in under ten minutes.

If you're an API or service provider building on Arbitrum: get indexed. Once you're integrated with PayAI, your endpoints become discoverable to every agent on every framework that connects through the PayAI facilitator.

The agentic web doesn't get built on one chain. It gets built on whichever chain a given team's stack already runs on, with a facilitator layer that makes those chains feel like one. Arbitrum joining PayAI is one more brick in that wall.

Let's build.

Frequently asked questions

Is x402 live on Arbitrum? Yes. As of today, the PayAI facilitator supports x402 payments on Arbitrum One (mainnet) and Arbitrum Sepolia (testnet) using USDC for settlement.

Do I need a new PayAI SDK to use Arbitrum? No. Existing x402 SDKs for Python, TypeScript, and Go support Arbitrum out of the box. On x402 v1 add arbitrum (or arbitrum-sepolia) to your endpoint's accepts array; on x402 v2 use the CAIP-2 chain ID eip155:42161 for Arbitrum One or eip155:421614 for Arbitrum Sepolia. The facilitator handles the rest.

Which tokens does x402 on Arbitrum settle in? USDC is the default settlement asset on Arbitrum One. The facilitator supports any EIP-3009 token — that includes USDC, PYUSD, USDP, FDUSD, EURC, and other stablecoins that implement transferWithAuthorization. x402 itself is token-agnostic at the protocol level.

What does x402 on Arbitrum cost? PayAI's facilitator pricing is identical across all networks: the first 10,000 settlements per month are free, then $0.001 per transaction. Arbitrum gas is paid separately and is typically a small fraction of a cent.

What other networks does PayAI support? PayAI is a multi-network x402 facilitator. Alongside Arbitrum, supported networks include Solana, Base, SKALE, Polygon, Avalanche, Sei, and X Layer, plus their respective testnets. The full list lives at docs.payai.network/x402/supported-networks.

Can AI agents pay for things on Arbitrum using x402? Yes. An agent holding an Arbitrum wallet with USDC can discover prices from x402 response headers, sign transactions, and access paid resources autonomously. This is the same agentic flow that already works on Solana and Base.

Follow @PayAINetwork for what ships next.