How to add custom RPC networks to MetaMask? (Network Configuration)

Accessing Network Settings in MetaMask

1. Open the MetaMask browser extension or mobile application and ensure you are logged into your wallet.

2. Click or tap the network selector, typically located at the top of the interface—this displays the current active network such as Ethereum Mainnet or Sepolia.

3. Scroll down and select “Add Network” or “Add a network manually”, depending on your MetaMask version.

4. Confirm that you are not on a phishing site by verifying the domain and checking for official MetaMask branding before entering any sensitive configuration details.

5. Avoid saving networks with mismatched chain IDs or incorrect RPC endpoints, as this may lead to transaction failures or asset misdirection.

Required Parameters for Custom RPC Configuration

1. Network Name: A human-readable label like “Arbitrum One” or “Base Mainnet”—used only for local identification inside MetaMask.

2. New RPC URL: The HTTPS endpoint provided by the blockchain’s infrastructure provider—must be stable and support JSON-RPC methods including eth_chainId and eth_blockNumber.

3. Chain ID: A unique integer identifier; must match exactly what the network uses—mismatches prevent signature verification and block synchronization.

4. Currency Symbol: Typically the native token ticker (e.g., “ETH”, “MATIC”, “AVAX”)—affects balance display but does not alter contract interactions.

5. Block Explorer URL: A public blockchain explorer link (e.g., https://arbiscan.io) used for transaction lookups—optional but highly recommended for transparency.

Verifying RPC Endpoint Authenticity

1. Cross-reference the RPC URL with documentation published on the official project website—not community forums or third-party GitHub gists.

2. Check TLS certificate validity in browser dev tools when accessing the RPC endpoint directly—expired or self-signed certificates indicate potential risk.

3. Test the endpoint using curl or a tool like Postman with a simple request: {'jsonrpc':'2.0','method':'eth_chainId','params':[],'id':1}—a valid response confirms basic connectivity.

4. Compare the returned chain ID from the RPC call against the canonical value listed on Chainlist.org or the network’s official developer portal.

5. Avoid endpoints hosted on domains containing suspicious subdomains, random strings, or known malicious TLDs like .xyz or .online without verified ownership.

Common Misconfigurations and Their Effects

1. Entering an HTTP instead of HTTPS RPC URL triggers MetaMask’s security warning and blocks addition in newer versions—always use encrypted transport.

2. Using a testnet chain ID (e.g., 80001) while pointing to a mainnet RPC causes wallet balances to appear zero or undefined due to state mismatch.

3. Setting an incorrect currency symbol leads to wrong unit interpretation during send transactions—even if ETH is sent, the UI might label it as “ARB” causing confusion.

4. Omitting the block explorer results in inability to verify on-chain confirmations, increasing reliance on MetaMask’s internal status indicators which lack contextual detail.

5. Copy-pasting RPC URLs from untrusted Telegram groups has led to multiple documented incidents where users unknowingly routed transactions through malicious relayers.

Frequently Asked Questions

Q: Can I add multiple custom networks with identical chain IDs?A: No. MetaMask treats chain ID as a primary key—duplicate entries will overwrite previous configurations without warning.

Q: Why does MetaMask show “Unknown Network” after adding a custom RPC?A: This occurs when the RPC endpoint fails to respond to eth_chainId or returns an unrecognized chain ID—verify connectivity and chain ID alignment.

Q: Is it safe to reuse the same RPC URL across different wallet extensions?A: Yes, provided the endpoint supports cross-origin requests and is operated by a trusted infrastructure provider—never share private API keys embedded in URLs.

Q: What happens if the custom RPC server goes offline?A: MetaMask will display “Not connected to network”, disable transaction submission, and show zero balances until a functional RPC endpoint is restored or replaced.