> For the complete documentation index, see [llms.txt](https://aboutcryptotalks.gitbook.io/aboutcrypto/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://aboutcryptotalks.gitbook.io/aboutcrypto/chainslist-check-chain-ids-before-importing-to-metamask.md). # chainslist: Check Chain IDs Before Importing to MetaMask chainslist helps you add the right EVM network to MetaMask by giving you a chain ID and RPC endpoint to check against the network your app requires. Match the ID before approving an import: the network name is a label, while the chain ID determines which chain the wallet signs transactions for. For a task you need to finish now, that check takes less time than diagnosing a wallet connected to the wrong network. ### Why check the chain ID before importing a network? The chain ID is the EIP-155 identifier used when signing a transaction. Ethereum Mainnet uses decimal 1, written 0x1 in hexadecimal; OP Mainnet uses decimal 10, or 0xa. A wallet can display any network name, so a familiar name alone does not establish that the signing chain is the one your app expects. Compare the app’s required chain ID with the proposed wallet configuration, including whether the app specifies a mainnet or a testnet. Do not substitute the value from net\_version: that RPC method reports a network ID, which is not necessarily the EIP-155 chain ID. The relevant RPC check is eth\_chainId, whose result is a hexadecimal string. ### Which network details need to agree? For a specific app, the chain ID and the RPC endpoint must identify the same intended chain. A chain list gives you candidate details, but the app or network operator’s published configuration is the reference for what the app expects. Check these fields together: * **Chain ID:** Compare the integer, accounting for decimal and hexadecimal notation. Decimal 10 and 0xa match; decimal 10 and 0x1 do not. * **RPC URL:** Check that the endpoint is intended for the same mainnet or testnet and uses HTTPS. The URL is where the wallet sends queries and transactions. * **Network name:** Use it to catch an obvious selection error, but do not treat a matching label as proof of the chain’s identity. * **Native currency and block explorer:** Check the displayed symbol against the network’s configuration. An explorer URL is optional, but a mismatched one is another reason to inspect the entry. For a concrete before-and-after check, suppose an app requires OP Mainnet, chain ID 10, while MetaMask is on Ethereum Mainnet, chain ID 1. Before importing, the wallet reports 0x1; after adding and selecting OP Mainnet, it should report 0xa. The account address may look the same on both networks, but adding the network does not move assets between them. ### How can I add a network from chainslist to MetaMask? First check whether MetaMask already offers the required network; if it does, select it and verify the chain ID. Otherwise, compare a directory entry’s ID and RPC URL with the app’s required network, then submit the network details to MetaMask and review its approval prompt. A one-click import starts that wallet request; approval remains your decision. At the protocol level, the request is wallet\_addEthereumChain. It supplies a hexadecimal chainId and one or more rpcUrls, and may include chainName, nativeCurrency and blockExplorerUrls. For the OP Mainnet example, the chainId value is 0xa; the chosen RPC must return 0xa from eth\_chainId. Adding a chain does not necessarily select it, so check the active network before returning to the app. Manual entry uses the same details when a directory entry is unavailable or you need a particular RPC provider. As rough task times, selecting a network already in the wallet takes under a minute, reviewing a directory import takes around one or two minutes, and entering and checking fields manually takes several minutes. The extra manual work is useful when your app requires a specific endpoint rather than any endpoint for that chain. ### What if the RPC and chain ID disagree? If an endpoint returns a different eth\_chainId from the proposed chainId, stop and find the correct endpoint or ID. For example, an RPC response of 0x1 cannot validate a request to add OP Mainnet as 0xa. A wallet following EIP-3085 rejects that mismatch; repeated attempts with the same values will not fix it. A matching response establishes what the endpoint claims, not that it is an honest view of the intended chain. An endpoint on a fork can report the same chain ID, so for an unfamiliar RPC, compare its address with the network operator’s published details and, where needed, compare a known block hash. If MetaMask says the chain already exists, inspect its saved RPC and select or update that network instead of trying to create a duplicate ID. ### Which EVM networks are listed, and are their RPC endpoints free? The directory covers EVM networks and provides their chain IDs and RPC endpoints; its live entries determine whether the particular mainnet or testnet your app needs is available. Search by the network’s precise name and confirm its ID rather than assuming that a similarly named testnet is interchangeable. Ethereum Mainnet’s ID 1 and OP Mainnet’s ID 10 are examples of the distinction to make, not a claim about the directory’s current inventory. Adding a network to a wallet has no blockchain transaction fee. A public RPC may be free for ordinary wallet use, but availability, rate limits and data handling depend on its operator; a private or metered endpoint may require a paid plan. Gas for a later transaction, and any fee for moving assets between chains, are separate costs. For one immediate app task, choose an endpoint that answers consistently and meets the app’s requirements before considering a dedicated provider. ### Can I use the directory with wallets other than MetaMask? Yes, if the wallet supports adding EVM networks with these details or accepts wallet\_addEthereumChain requests. A wallet that does not accept the request may still let you enter the chain ID and RPC URL manually. Wallets can require different optional fields, so use the same verified chain identity while following that wallet’s own import process. The chain list is most useful once you know the chain ID your app requires and have checked the proposed RPC against it. For the import step, use [chainslist](https://chainslist.org) to find the network details and add the network to MetaMask or another compatible wallet in one click. I would approve the wallet prompt only when its chain ID matches the app’s requirement, then confirm that the wallet has selected that chain. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation by asking a question. Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters: ``` GET https://aboutcryptotalks.gitbook.io/aboutcrypto/chainslist-check-chain-ids-before-importing-to-metamask.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is what the user is ultimately trying to achieve, the reason they need the answer. 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