# Arc developer reference

Arc mainnet is chain ID 5042 (0x13b2); its public RPC is https://rpc.mainnet.arc.io, its block explorer is https://explorer.arc.io (Blockscout), and gas is paid in USDC.

Each answer links its source. Projects come from the [Arc ecosystem directory](https://builder.registrai.cc/ecosystem/), last reviewed 2026-11-01. Chain facts: [Arc blockchain: facts with sources](https://builder.registrai.cc/arc/facts/).

- [What is the Arc mainnet chain ID and RPC URL?](#chain-id-rpc)
- [How do I deploy a smart contract on Arc?](#deploy)
- [What block explorer does Arc use?](#explorer)
- [How do I accept USDC payments in my app on Arc?](#accept-usdc)
- [Is there an MCP server for Arc blockchain data?](#mcp)
- [How can an AI agent pay for an API with USDC on Arc using x402?](#x402)

## What is the Arc mainnet chain ID and RPC URL?

Arc mainnet's chain ID is 5042 (0x13b2) and its public RPC URL is https://rpc.mainnet.arc.io, run by Circle with no API key. ([source](https://docs.arc.io/arc/references/connect-to-arc))

| Setting | Value |
| --- | --- |
| Network name | Arc Mainnet |
| Chain ID | 5042 (0x13b2) |
| RPC | `https://rpc.mainnet.arc.io` |
| WebSocket | `wss://rpc.mainnet.arc.io` |
| Currency | USDC, 18 decimals as the native gas token (i: The ERC-20 interface of the same USDC is at 0x3600000000000000000000000000000000000000 with 6 decimals; Arc's docs say not to show the two as separate balances.) |
| Explorer | [https://explorer.arc.io](https://explorer.arc.io) |

### Public RPC endpoints

8 endpoints: 7 answer without a key.

| Provider | HTTP endpoint | Key | Up, 24 h | Up, 7 days | Latency, 24 h median | Blocks behind | Source |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Arc (Circle) | `https://rpc.mainnet.arc.io` | None | 100% | 100% | 34 ms | 1 | [source](https://docs.arc.io/arc/references/rpc-endpoints) |
| [Blockdaemon](https://builder.registrai.cc/ecosystem/blockdaemon/) | `https://rpc.blockdaemon.mainnet.arc.io` | None | 100% | 100% | 14 ms | 1 | [source](https://docs.arc.io/arc/references/rpc-endpoints) |
| [dRPC](https://builder.registrai.cc/ecosystem/drpc/) | `https://rpc.drpc.mainnet.arc.io` | None | 100% | 100% | 26 ms | 1 | [source](https://docs.arc.io/arc/references/rpc-endpoints) |
| [QuickNode](https://builder.registrai.cc/ecosystem/quicknode/) | `https://rpc.quicknode.mainnet.arc.io` | None | 100% | 100% | 34 ms | 1 | [source](https://docs.arc.io/arc/references/rpc-endpoints) |
| [PublicNode (Allnodes)](https://builder.registrai.cc/ecosystem/allnodes/) | `https://arc-rpc.publicnode.com` | None | 100% | 100% | 37 ms | 0 | [source](https://arc.publicnode.com/) |
| [thirdweb](https://builder.registrai.cc/ecosystem/thirdweb/) | `https://5042.rpc.thirdweb.com` | None | Rate-limited (i: Every check from our server in the last 24 h got HTTP 429, the provider's rate limit for use without a key. It answers from other networks; a key lifts the limit.) | – | – | – | [source](https://thirdweb.com/arc) |
| [Tenderly](https://builder.registrai.cc/ecosystem/tenderly/) | `https://arc.gateway.tenderly.co` | None | 100% | 100% | 18 ms | 1 | [source](https://docs.tenderly.co/node-rpc/overview) |
| [Alchemy](https://builder.registrai.cc/ecosystem/alchemy/) | `https://arc-mainnet.g.alchemy.com/v2/YOUR_API_KEY` | API key | Not measured | – | – | – | [source](https://docs.arc.io/arc/references/rpc-endpoints) |

Checked hourly by Registrai; last check 8 Nov 2026, 23:17 UTC, 6 of 7 endpoints up, 1 rate-limited. (i: Every hour, from one server, Registrai calls eth\_chainId once and eth\_blockNumber 3 times, 1 s apart, on each endpoint that needs no key, all endpoints at the same time. A check is up when the chain ID is 5042 and at least 2 of the 3 block-number calls answer within 5 s. Latency is the median time of those calls, so it includes the network path from our server; from elsewhere it differs. An HTTP 429 (the provider's rate limit for use without a key) is shown as rate-limited and left out of uptime. Blocks behind: the highest block any endpoint returned in the last round minus this endpoint's; a block or two is timing, not lag.) Data: [rpc.json](https://builder.registrai.cc/arc/developers/rpc.json). Endpoints listed 2026-11-04; Arc's own list: [RPC endpoints](https://docs.arc.io/arc/references/rpc-endpoints).

## How do I deploy a smart contract on Arc?

Arc is EVM-compatible, so Solidity contracts deploy as on Ethereum, with gas paid in USDC; Arc's docs use Arc Foundry (arc-forge, arc-cast, arc-anvil), a fork of Foundry that supports Arc's differences from Ethereum. ([source](https://docs.arc.io/arc/tutorials/deploy-on-arc), [EVM differences](https://docs.arc.io/arc/references/evm-differences))

1. Install Arc Foundry from its [releases](https://github.com/circlefin/arc-foundry/releases) ([how-to](https://docs.arc.io/arc/tutorials/install-arc-foundry)).
2. Fund the deploying address with USDC on Arc for gas: [how to get USDC onto Arc](https://builder.registrai.cc/arc/get-usdc/).
3. Deploy: `arc-forge create src/Counter.sol:Counter --rpc-url https://rpc.mainnet.arc.io --private-key $PRIVATE_KEY --broadcast`
4. Verify the source on the explorer: `arc-forge verify-contract` with `--verifier blockscout` (Arc's tutorial shows it against the testnet explorer's `/api/`), or submit it on [explorer.arc.io](https://explorer.arc.io).

Arc's tutorial runs these steps on testnet (chain ID 5042002, faucet USDC); on mainnet the RPC and chain ID above apply.

### Developer tools live on Arc

| Project | What it does on Arc | Status | Evidence |
| --- | --- | --- | --- |
| [Allium](https://builder.registrai.cc/ecosystem/allium/) | Onchain data platform; its data catalog and APIs index Arc (raw, decoded, DEX, lending, stablecoin and RWA tables). | Live on mainnet | [evidence](https://docs.allium.so/changelog/overview) |
| [Crossmint](https://builder.registrai.cc/ecosystem/crossmint/) | Stablecoin and wallet infrastructure for enterprises. | Live on mainnet | [evidence](https://docs.crossmint.com/introduction/supported-chains) |
| [DFNS](https://builder.registrai.cc/ecosystem/dfns/) | Wallet-as-a-service and key management platform for banks, fintechs and businesses. | Live on mainnet | [evidence](https://www.arc.io/ecosystem/dfns) |
| [Dune](https://builder.registrai.cc/ecosystem/dune/) | Onchain data query platform; it indexes Arc under the arc schema (blocks, transactions, logs, traces, decoded contracts). | Live on mainnet | [evidence](https://docs.dune.com/data-catalog/evm/arc/overview) |
| [HIFI](https://builder.registrai.cc/ecosystem/hifi/) | API platform for moving money across fiat rails and stablecoins, covering cross-border payments, payouts and stablecoin minting. | Live on mainnet | [evidence](https://www.arc.io/ecosystem/hifi) |
| [Lagoon](https://builder.registrai.cc/ecosystem/lagoon/) | Vault infrastructure for onchain asset management built on the ERC-7540 asynchronous vault standard. | Live on mainnet | [evidence](https://explorer.arc.io/address/0xf185b0083fd2446d3742fe3f4c3175b7e306752b) |
| [Meter](https://builder.registrai.cc/ecosystem/meter/) | Pay-per-call API gateway: a caller pays a registered endpoint in USDC through the MeterRegistry contract and sends the transaction hash as… | Live on mainnet | [evidence](https://explorer.arc.io/address/0x423b8701da3a251a3a3fc2d241b71e8d05744c91) |
| [Pimlico](https://builder.registrai.cc/ecosystem/pimlico/) | Account abstraction infrastructure providing ERC-4337 bundler and paymaster services. | Live on mainnet | [evidence](https://docs.pimlico.io/guides/supported-chains) |
| [Team Finance](https://builder.registrai.cc/ecosystem/team-finance/) | Token tooling platform for creating tokens and for locking liquidity, team tokens and NFTs, with vesting, staking pools, airdrops and… | Live on mainnet | [evidence](https://www.team.finance/arc) |
| [Thirdweb](https://builder.registrai.cc/ecosystem/thirdweb/) | Web3 developer platform for wallets, payments, bridging and tokens. | Live on mainnet | [evidence](https://thirdweb.com/arc) |
| [ZeroDev](https://builder.registrai.cc/ecosystem/zerodev/) | Smart account infrastructure covering account abstraction, gas sponsorship, session keys and embedded wallets. | Live on mainnet | [evidence](https://docs.zerodev.app/sdk/faqs/chains) |

## What block explorer does Arc use?

Arc uses Blockscout as its block explorer, at https://explorer.arc.io for mainnet. ([source](https://docs.arc.io/arc/references/rpc-endpoints))

### Indexers and data

| Project | What it does on Arc | Status | Evidence |
| --- | --- | --- | --- |
| [Blockscout](https://builder.registrai.cc/ecosystem/blockscout/) | Open-source blockchain explorer. | Live on mainnet | [evidence](https://explorer.arc.io) |
| [Goldsky](https://builder.registrai.cc/ecosystem/goldsky/) | Blockchain data and automation platform. | Live on mainnet | [evidence](https://docs.goldsky.com/chains/arc) |
| [Allium](https://builder.registrai.cc/ecosystem/allium/) | Onchain data platform; its data catalog and APIs index Arc (raw, decoded, DEX, lending, stablecoin and RWA tables). | Live on mainnet | [evidence](https://docs.allium.so/changelog/overview) |
| [Dune](https://builder.registrai.cc/ecosystem/dune/) | Onchain data query platform; it indexes Arc under the arc schema (blocks, transactions, logs, traces, decoded contracts). | Live on mainnet | [evidence](https://docs.dune.com/data-catalog/evm/arc/overview) |
| [Alchemy](https://builder.registrai.cc/ecosystem/alchemy/) | Node, data and wallet API provider. | Live on mainnet | [evidence](https://www.alchemy.com/arc) |
| [DefiLlama](https://builder.registrai.cc/ecosystem/defillama/) | DeFi data aggregator that tracks Arc as a chain (chain ID 5042) with TVL and protocol listings. | Live on mainnet | [evidence](https://api.llama.fi/v2/chains) |

Arc's docs also list Envio, Pinax, The Graph, thirdweb and Zerion as data indexers ([source](https://docs.arc.io/arc/tools/data-indexers)). Registrai's own [data API](https://builder.registrai.cc/data-api/) serves app payments, the Arc indices and the directory.

## How do I accept USDC payments in my app on Arc?

Two ways: receive USDC directly to your own address and confirm each payment from USDC's transfer events, or take payments through a provider live on Arc.

- Directly: USDC is Arc's native token (18 decimals) and also an ERC-20 at `0x3600000000000000000000000000000000000000` (6 decimals); Arc's docs describe which events to watch ([USDC system events](https://docs.arc.io/arc/references/usdc-system-events)) and a checkout flow ([eCommerce checkout](https://docs.arc.io/build/ecommerce)).
- Per request, for APIs and AI agents: x402 ([below](#x402)).

### Payment providers for developers

| Project | What it does on Arc | Status | Evidence |
| --- | --- | --- | --- |
| [HIFI](https://builder.registrai.cc/ecosystem/hifi/) | API platform for moving money across fiat rails and stablecoins, covering cross-border payments, payouts and stablecoin minting. | Live on mainnet | [evidence](https://www.arc.io/ecosystem/hifi) |
| [Meter](https://builder.registrai.cc/ecosystem/meter/) | Pay-per-call API gateway: a caller pays a registered endpoint in USDC through the MeterRegistry contract and sends the transaction hash as… | Live on mainnet | [evidence](https://explorer.arc.io/address/0x423b8701da3a251a3a3fc2d241b71e8d05744c91) |

Payment apps already taking USDC on Arc: [apps that accept USDC on Arc](https://builder.registrai.cc/arc/apps-that-accept-usdc/).

## Is there an MCP server for Arc blockchain data?

Yes. Registrai runs a read-only MCP server for Arc blockchain data at https://builder.registrai.cc/api/mcp (Streamable HTTP, no sign-in or key), listed in the MCP registry as cc.registrai/arc-data. It serves the same data as the API: stablecoin payments per app, the Arc indices, the ecosystem directory and Arc chain figures. [Tools and setup](https://builder.registrai.cc/data-api/)

`claude mcp add --transport http registrai-arc https://builder.registrai.cc/api/mcp`

Arc's documentation has its own MCP server at `https://docs.arc.io/mcp`; it searches the docs and does not serve chain data ([source](https://docs.arc.io/ai/mcp)).

## How can an AI agent pay for an API with USDC on Arc using x402?

The API answers HTTP 402 with its price; the agent signs a USDC payment authorization (EIP-3009) and retries the request with it attached. On Arc, Circle Gateway Nanopayments settles these in batches, gas-free for the agent, after a one-time USDC deposit. ([x402](https://developers.circle.com/gateway/nanopayments/concepts/x402), [Nanopayments](https://developers.circle.com/gateway/nanopayments); Arc is supported: [Gateway blockchains](https://developers.circle.com/gateway/references/supported-blockchains))

Circle's sample agent that pays API endpoints in USDC on Arc: [circlefin/arc-nanopayments](https://github.com/circlefin/arc-nanopayments).

### x402 services on Arc

| Project | What it does on Arc | Status | Evidence |
| --- | --- | --- | --- |
| [ArcLens](https://builder.registrai.cc/ecosystem/arclens/) | Arc ecosystem directory and data platform with project listings, campaigns, an explorer and a pay-per-call AI agent API over x402. | Live on mainnet | [evidence](https://github.com/arclens-app/arclens) |
| [Arclight](https://builder.registrai.cc/ecosystem/arclight/) | Also runs an x402 payment facilitator. | Live on mainnet | [evidence](https://arclight.finance/docs/how-it-works) |
| [BlockRun](https://builder.registrai.cc/ecosystem/blockrun/) | Pay-per-call gateway to AI models and data APIs, paid in USDC on Arc through the x402 protocol. | Live on mainnet | [evidence](https://arc.blockrun.ai/) |

Announced: [Orthogonal](https://builder.registrai.cc/ecosystem/orthogonal/)

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