To choose chainslist network details that work, match the intended EVM network’s chain ID to a working RPC endpoint, then add and select that chain in your wallet. For that lookup and wallet request, chainslist provides the chain ID and RPC details and lets you add the network to MetaMask or another compatible wallet in one click.
Three checks settle most stalled setups:
-
Identify the exact mainnet or testnet by chain ID; a familiar network name is insufficient.
-
Check that the RPC endpoint reports that same ID and responds to recent block queries.
-
After adding the network, confirm it is the wallet’s active chain before retrying.
The chainslist directory covers EVM networks
Its scope is EVM networks with chain IDs and RPC endpoints: mainnets, layer 2 networks, sidechains, and testnets where entries exist. The exact set of entries can change, so look up the chain your application requires rather than assuming that a similarly named network is interchangeable. A non-EVM network needs a different wallet and connection method.
The distinction matters even within one project. Optimism’s network documentation identifies OP Mainnet as chain ID 10 and OP Sepolia as 11155420. If an application expects OP Mainnet, adding the testnet gives you a working wallet connection to the wrong chain; balances and contracts will appear different because they are different networks.
Treat a chain list entry as a set of configuration claims, not proof that its endpoint is current or trustworthy. Compare the chain ID and network name with the network operator’s published details when a transaction matters. A directory can help you find the fields, while the wallet and RPC endpoint still determine what happens when you connect.
Chain ID and RPC agreement decide whether an entry works
The decisive technical check is whether the RPC endpoint’s eth_chainId response equals the ID you intend to add. Wallet requests use a hexadecimal chain ID: OP Mainnet’s decimal 10 is 0xa. Its published public RPC endpoint should therefore answer eth_chainId with 0xa; an answer for another ID means the URL points elsewhere, regardless of the name beside it.
The Ethereum Improvement Proposals’ EIP-3085 describes the wallet_addEthereumChain request. It carries a chainId and RPC URL, and may include a chain name, native currency and block explorer. For OP Mainnet, the relevant currency symbol is ETH; its operator publishes the other network fields, so check them before approving a wallet prompt.
A matching ID is necessary, but it does not establish endpoint quality. Try eth_blockNumber twice, several seconds apart: a timeout, an error, or a persistently stale height suggests that the endpoint may fail balance reads, gas estimates or transaction submission. A wallet may reject an endpoint it cannot validate even when the directory entry itself looks correct.
Choose the add method by what you need to control
Use a wallet’s existing network entry when it already has the correct chain ID and a working RPC connection. If the network is absent, a directory request saves you from transcribing the fields; inspect the wallet’s proposed chain ID and RPC URL before approving it. Use manual entry when you need a particular endpoint, such as a private RPC URL issued for your account.
Before: a wallet rejects an attempt to add OP Mainnet because the supplied RPC answers with a different chain ID. After: you replace that URL with an endpoint that returns 0xa, approve the network details, and select OP Mainnet. The change fixes the identity mismatch; it does not move assets or alter transactions already sent on another chain.
If the wallet says the chain already exists, adding a second copy is usually the wrong operation. Switch to the existing chain or edit its RPC URL if that wallet permits it. EIP-3085 does not require an added chain to become active automatically; EIP-3326 defines a separate wallet_switchEthereumChain request for switching.
Listed RPC endpoints can be free, with usage limits
Some listed public RPC endpoints accept requests without an API key or direct charge, but a listing does not promise free or unlimited use. Optimism’s documentation, for example, says its public RPC URLs are rate limited. Endpoints from providers such as Infura or Alchemy may instead require credentials, with allowances and charges set by the provider.
For occasional wallet use, a responsive public endpoint may be sufficient. For repeated queries or an application that depends on reliable reads, compare rate limits, latency, supported methods and whether the provider retains request data. RPC access and transaction cost are separate: adding a network does not fund the wallet, and a transaction still needs the chain’s native gas token.
A failed add needs a targeted retry
Match the next action to the failure. If no wallet prompt appears, check that the intended wallet is connected and able to receive the request. If the prompt reports invalid network details, compare the proposed ID with eth_chainId and check the RPC URL; if the network was added but the application still objects, select it as the active chain and reconnect.
If reads work but submissions fail or remain pending, check the endpoint’s current block height, the wallet’s native-token balance and the transaction status on the correct chain. Change your choice of RPC endpoint when those checks point to stale data or rate limiting. Change your choice of network only when the application or network operator specifies a different chain ID.