A user downloads the MetaMask wallet extension and sees Ethereum and a handful of major networks already configured. But they want to interact with Arbitrum, Polygon, or Base—networks that their counterparties mention frequently but that do not appear in the default list. The solution is not to switch wallets or create a separate account. The metamask wallet extension supports custom network configuration, which allows adding any EVM-compatible blockchain in minutes.

This capability transforms MetaMask from a single-chain application into a genuine multichain wallet. The process itself is straightforward: users can manually enter network parameters or use community-maintained chainlists that populate the form automatically. However, accuracy matters. A misconfigured network can cause transactions to fail, display incorrect balances, or send funds to the wrong destination entirely. Understanding the underlying mechanics prevents these errors and helps users verify that network information comes from reliable sources.

Understanding why default networks are limited

MetaMask ships with Ethereum mainnet, Sepolia testnet, and a few additional networks pre-loaded. This conservative approach protects new users from accidentally sending funds to an unfamiliar chain, while keeping the interface clean and reducing initial confusion. However, Arbitrum, Polygon, Linea, BNB Chain, Base, and dozens of other EVM-compatible networks are not included by default, despite being widely used and fully supported by the MetaMask wallet extension.

The reason is practical rather than technical. MetaMask’s developers cannot anticipate every network a user might eventually need, nor should the application burden every user with a comprehensive list of hundreds of chains. Instead, the extension provides a custom network configuration feature that treats all EVM networks—whether pre-configured or user-added—identically once they are registered. This design keeps the default experience simple while preserving full flexibility.

The precondition is that a network must be EVM-compatible. This means it implements the Ethereum Virtual Machine specification, so MetaMask accounts (derived from a single seed phrase) work across all these chains. Solana, for example, is supported by MetaMask but requires a separate signing mechanism and is not configured through the custom network interface. Bitcoin is similarly supported as a native option within the extension, but it does not use the EVM network configuration system.

Users who want to experiment with multiple EVM chains benefit from understanding this unified model. A single private key controls accounts on Ethereum, Arbitrum, Polygon, and every other EVM network simultaneously. Switching between networks changes only which blockchain the extension communicates with; it does not require importing different keys or creating separate wallets. This is both a convenience and a responsibility: managing funds on one chain is not fundamentally different from managing them on another, from the wallet’s perspective.

The essential parameters for custom network configuration

Adding a custom network to the metamask wallet extension requires five core pieces of information. The first is the Network Name, a display label that appears in the dropdown menu. This can be anything useful to the user—”Arbitrum One,” “Polygon Mainnet,” or a custom shorthand. The second is the New RPC URL, which is the endpoint that MetaMask uses to communicate with the blockchain. This is the most critical parameter because an incorrect or unavailable endpoint will prevent the wallet from querying balances, sending transactions, or displaying transaction history.

The third parameter is the Chain ID, a numerical identifier that distinguishes one EVM network from another. Ethereum mainnet has Chain ID 1, Arbitrum One is 42161, and Polygon is 137. If this number is wrong, transactions may be rejected or routed to an entirely different network. The fourth piece of information is the Currency Symbol, typically ETH for Ethereum-derived networks but sometimes a network-specific token like MATIC for Polygon or ARB for Arbitrum. This is purely a display field and does not affect transaction functionality.

The fifth and optional parameter is the Block Explorer URL, such as Etherscan for Ethereum or Arbiscan for Arbitrum. When configured, clicking a transaction hash in MetaMask’s activity log opens the corresponding page on that explorer, allowing users to verify the transaction on the public ledger. This is not required for the network to function, but it is useful for checking transaction status, confirming fees, and debugging failed transactions.

The multichain wallet architecture means that all five parameters must be accurate and internally consistent. An RPC URL pointing to a legitimate service but with the wrong Chain ID will cause MetaMask to believe it is on one network when it is actually interacting with another. Similarly, a correct RPC but an incorrect Block Explorer URL will not break functionality, but it will send users to the wrong explorer when they try to verify their transactions, creating confusion and potential security errors.

Finding reliable network parameters and chainlists

The easiest way to add a network is to use a community-maintained chainlist such as chainlist.org. This service aggregates verified RPC endpoints, Chain IDs, block explorers, and other parameters for hundreds of EVM networks. A user searches for “Arbitrum” or “Polygon,” selects the desired network from the results, and clicks “Add to MetaMask.” The extension then pre-fills all required fields, reducing the chance of manual entry errors.

Using chainlist does require trust in the service itself. Chainlist is community-driven, meaning network information is submitted and updated by users rather than official sources. In practice, this system works well because incorrect parameters are quickly reported and corrected. However, users should verify critical information—particularly the Chain ID and official RPC endpoint—against the network’s own documentation. Official sources include Arbitrum’s bridge documentation, Polygon’s setup guides, and similar resources from each network’s core team.

If manually entering parameters, users should cross-reference at least two independent sources. For Arbitrum One, the official RPC endpoint is listed on Arbitrum’s website, and the same endpoint appears consistently across chainlist.org and other aggregators. A mismatch should trigger skepticism. Some networks publish “public” RPC endpoints that may have rate limits or unavailability windows; production users often prefer paid third-party services such as Infura, Alchemy, or QuickNode that offer more reliable uptime and higher rate limits.

The Block Explorer URL should point to a service that actually tracks transactions on that network. Arbitrum transactions can be viewed on Arbiscan.io (the Arbitrum-specific variant of Etherscan), while Polygon uses Polygonscan. Mismatching a Block Explorer with the wrong network—such as using Etherscan for an Arbitrum transaction—will display “Transaction not found” and confuse users into thinking their transaction failed when it actually succeeded on the correct chain.

Step-by-step process for adding a network via MetaMask settings

Users can add a custom network directly within MetaMask without external tools, though this requires manual entry of all parameters. Open the extension, click the menu icon (three horizontal lines), and select “Settings.” Then choose “Networks” from the left sidebar. At the bottom of the network list, there is an “Add Network” button. Clicking it opens a form with fields for Network Name, New RPC URL, Chain ID, Currency Symbol, and Block Explorer URL.

Fill in each field carefully. For Arbitrum One, the form would include the network name “Arbitrum One,” the official RPC endpoint (such as https://arb1.arbitrum.io/rpc), the Chain ID 42161, the currency symbol ARB (or ETH if the user prefers), and the block explorer URL https://arbiscan.io. Some users prefer the browser’s address bar to copy-paste these details, reducing the risk of typos. Once all fields are completed, click “Save” and the network will be added to the dropdown menu.

After saving, the network appears immediately in the dropdown selector alongside Ethereum, Sepolia, and any previously configured networks. Users can now switch to Arbitrum, see their wallet balance on that chain, and authorize transactions. The metamask wallet extension automatically displays the network name, token symbol, and RPC status in the interface, so users can quickly verify they are on the correct chain before confirming a transaction.

If a network fails to respond or displays an error, the first troubleshooting step is to verify the RPC URL. Some endpoints are rate-limited or may be temporarily unavailable. Switching to a different public RPC (from chainlist) or upgrading to a paid service such as Infura can resolve the issue. If the Chain ID is incorrect, MetaMask may accept the network but then reject all transactions or display balances from the wrong blockchain. Double-checking against the official network documentation is the surest way to resolve these errors.

Common networks ready to add: Arbitrum, Polygon, Base, and others

Arbitrum One is an Ethereum Layer 2 scaling solution designed to reduce transaction costs and increase throughput. The Chain ID is 42161, and the official RPC is https://arb1.arbitrum.io/rpc. Polygon (formerly Matic) is a sidechain offering faster and cheaper transactions than Ethereum, with Chain ID 137 and RPC https://polygon-rpc.com. Base is a newer Layer 2 built on Optimism technology, with Chain ID 8453 and RPC https://mainnet.base.org. BNB Chain is the blockchain behind the Binance exchange, with Chain ID 56 and RPC https://rpc.ankr.com/bsc.

Linea is a zero-knowledge rollup (zkEVM) with Chain ID 59144 and RPC https://rpc.linea.build. Each network has subtle differences: Arbitrum uses optimistic rollup technology, Base and other Optimism-derived chains use the same mechanism, Linea uses zero-knowledge proofs, and Polygon uses a sidechain model. These technical differences do not affect how MetaMask interacts with the network, but they do influence transaction fees, confirmation times, and security assumptions. Users should understand whether they are using a Layer 2 (directly secured by Ethereum’s settlement) or a separate chain before sending significant value.

The multichain wallet model means that a single seed phrase controls accounts on all these networks simultaneously. A user’s Ethereum address (derived from their MetaMask recovery phrase) will be identical on Arbitrum, Polygon, Base, and every other EVM chain. This simplicity is powerful: no need to import separate keys or remember different addresses. However, it also means that compromising a recovery phrase exposes funds across every EVM network the user has added, not just Ethereum.

Most of these networks maintain their own block explorers and official documentation. Users should bookmark the explorer URL relevant to each network they use regularly, both for the MetaMask configuration and for quick reference when verifying transactions. Adding a network does not automatically make MetaMask interact with it; the user must explicitly switch to the network using the dropdown, see their balance, and authorize the transaction. This explicit step is a safety feature, preventing accidental transactions on the wrong chain.

Hardware wallet integration across custom networks

MetaMask supports hardware wallet devices such as Ledger and Trezor, which keep private keys offline and require physical confirmation of transactions. When a custom network has been added to the extension, hardware wallet users can interact with that network just as they would with Ethereum. The connection flow remains the same: MetaMask communicates with the hardware device, the user physically confirms the transaction, and the signed transaction is then broadcast to the custom network’s RPC endpoint.

This integration extends the security model of a hardware wallet across all EVM networks supported by the MetaMask wallet extension. A user can add Arbitrum, approve a transaction on their Ledger device, and benefit from the same security guarantees as a transaction on Ethereum mainnet. The hardware device is responsible for verifying the destination address, transaction amount, and network parameters before the user confirms—though users must still examine the hardware device’s display carefully, as sophisticated attacks can attempt to hide the true destination or amount.

One additional consideration is that some older hardware wallet firmware versions may not recognize newer EVM networks. A user adding Base or Linea might find that their hardware device does not display the network name on its screen during transaction confirmation. In these cases, the transaction may still succeed (MetaMask will broadcast it correctly), but the user will see less information on the device itself. Updating hardware firmware before adding new networks can prevent this limitation.

Security and verification best practices when configuring networks

Adding a network is an important security decision because an incorrect RPC endpoint could theoretically display false balances, intercept transaction details, or manipulate what the user sees on screen. A compromised RPC endpoint is not an impenetrable attack surface—MetaMask still validates transaction signatures and the blockchain itself will reject invalid transactions—but it could deceive a user about their balance or transaction status. Therefore, users should verify network parameters from multiple independent sources.

The most reliable sources are the official documentation and websites of the network itself. Arbitrum’s official site, Polygon’s developer documentation, and Base’s launch materials all publish the correct RPC endpoints and Chain IDs. Public services like Infura and Alchemy are also trustworthy because they are well-known companies with incentive to provide correct information and are audited by security researchers. Chainlist is useful as a time-saver, but its community-driven model means users should always cross-check critical parameters, especially for less popular networks.

After adding a network, users should test it with a small transaction before sending significant value. Sending a tiny amount of the network’s native token to a known address confirms that the network is correctly configured, the RPC is responding, and the Block Explorer URL works. If something is wrong, a small loss is far preferable to discovering the problem after moving a large balance. This habit is especially important for users new to EVM networks or adding a network for the first time.

One additional safeguard is to disable or remove unused custom networks from the dropdown menu. If a user added a network months ago and no longer uses it, removing it reduces visual clutter and the chance of accidentally switching to it. Networks can be added again at any time, so removing an unused configuration is not a destructive action. The important networks—the ones the user regularly interacts with—can be left in place, and they will continue to work as long as the RPC endpoint remains available.

Troubleshooting failed network additions and common errors

The most frequent error is an invalid RPC URL. This might occur if the user accidentally includes a typo, uses an outdated endpoint, or copies a service that has changed its API structure. MetaMask will attempt to validate the RPC URL when the user clicks “Save.” If the endpoint is unreachable or returns an error, MetaMask may display a warning or reject the addition. In this case, verify the RPC URL against the network’s official documentation and try again.

A second common issue is an incorrect Chain ID. If the Chain ID does not match the network’s actual identifier, MetaMask may accept the configuration but then behave unpredictably. For example, if a user accidentally enters Chain ID 1 (Ethereum) while using an Arbitrum RPC, MetaMask will believe it is on Ethereum even though the RPC is actually serving Arbitrum requests. This mismatch can cause balance lookups to fail or transactions to be rejected. The fix is to correct the Chain ID in the network settings and verify against the official network documentation.

If a network is added but MetaMask shows “No balance” or “Unable to fetch balance,” the RPC endpoint may be temporarily unavailable or rate-limited. Try switching to an alternative public RPC from chainlist or waiting a few minutes before retrying. If the problem persists, verify that the Chain ID is correct and that the Block Explorer URL (if configured) corresponds to the actual network.

In rare cases, a user may accidentally use a testnet RPC for a mainnet network, or vice versa. A testnet RPC (such as Arbitrum’s Sepolia testnet) will require testnet tokens rather than mainnet tokens, and transactions will not be visible on the mainnet Block Explorer. To verify, check the Block Explorer URL: if transactions appear there after a few minutes, the network is configured correctly; if not, the RPC may be pointing to a testnet or a different network entirely.

Moving beyond Ethereum: the broader multichain experience

Once a user has successfully added Arbitrum, Polygon, and one or two other networks, they begin to appreciate the multichain wallet model that MetaMask enables. Instead of maintaining separate wallets for different chains or relying on centralized exchanges to move tokens between networks, users can hold assets directly across multiple EVM chains within a single extension. The same seed phrase, the same address, the same interface—but with access to a much larger ecosystem of decentralized applications and liquidity pools.

This capability is not unique to MetaMask, but MetaMask’s size and dominance make it the de facto standard. Most decentralized applications on Arbitrum, Polygon, and Base are designed to work seamlessly with a metamask wallet extension. A user connecting their wallet to a Uniswap instance on Polygon, for example, will see a familiar MetaMask dialog asking to approve the connection and sign transactions. The user’s funds remain under their control, and their recovery phrase is the only key that can authorize withdrawals.

However, multichain exposure also introduces multichain risk. Compromising a recovery phrase exposes funds across every EVM network the user has configured, not just Ethereum. Similarly, a user who interacts with many applications across many networks increases their surface area for phishing, smart contract bugs, and other threats. The security practices that apply to Ethereum—strong passwords, hardware wallet use, caution with approvals, careful phishing defense—become even more important as users expand across multiple chains.

The metamask wallet extension continues to evolve, with ongoing improvements to network switching, transaction clarity, and security warnings. As EVM ecosystems mature and new chains launch, users can add them with confidence, knowing that the underlying model is consistent and well-established. The ability to add custom networks is not just a convenience feature; it is the mechanism that allows MetaMask to remain relevant as the blockchain landscape fragments into dozens of competing Layer 2 solutions, sidechains, and alternative EVM implementations.