A user asks: How do I add custom networks like Binance Smart Chain, Polygon or Avalanche to MetaMask?**
How to Add Custom Networks To MetaMask
by CryptoHamilton
This is an excellent question because many users are not aware of different custom networks with lower gas fees or how to set them up on MetaMask.
Some incorrectly think that MetaMask sets the high fees and tries to rip them off. In reality, it’s market demand for a blockchain network that sets the prices. MetaMask has no control over this. Plus, we 
our users.
If things get expensive in one network, you can go to another with possibly lower fees, while Ethereum begins to scale and lower costs.
TL;DR:
- Custom networks are Ethereum compatible networks.
- Gas is determined by a network’s demand, not by MetaMask or any wallet provider.
- Different networks have different gas fees based on their design and demand.
- Sidechains and Layer-2 solutions are types of custom networks you can add to MetaMask. They may have lower gas fees at the expense of decentralization or security.
- Sidechains and Layer-2 solutions mainly differ on how their blocks are validated.
- Example of custom networks are Binance Smart Chain, Polygon (MATIC), Huobi ECO Chain, Avalanche, and xDai.
After successfully installing (or re-installing) MetaMask and securing your secret recovery phrase (aka seed phrase), you decide you want to interact with custom networks.
How do you do this? Well, first of all, what are custom networks?
What are custom networks?
Custom Networks are non-Ethereum networks that are EVM compatible (Ethereum Virtual Machine). They are based on Ethereum but are not Ethereum. Think of them as siblings or relatives of Ethereum. They share many of the same features but differ in some key ways.
Their similarities are in that they execute smart contracts in a similar manner. The differences can lie in reaching a consensus (agreement between the different nodes) and how much data can be placed in their blockchain’s block.
Since they are Ethereum based networks, your addresses will be the same across all the networks. That means that a single secret recovery phrase (aka seed phrase) can access your assets across all your accounts and networks.
Reminder: Never share your seed phrase, aka secret recovery phrase.
Why do these blockchains differ?
Different blockchains can be used for different needs. As the industry evolves, many will specialize in different use cases. Broadly speaking, blockchains can specialize via three avenues: scalability (high throughput), decentralization, or security. This is known as the security trilemma, and it states that blockchains can have 2 of 3 properties, but not all three. This is called the security trilemma.
A blockchain-based video game with a high volume of small transactions will have different needs than a borrowing/lending protocol. The video game will need high throughput and be willing to sacrifice a bit of security. The borrowing and lending protocol would value security and decentralization over higher throughput. The real-world effects of this trade-off are that less scalable blockchains lead to higher gas but are more secure.
Each network typically has its own custom token used to pay for network activity. Ethereum uses ETH (Ether). Binance uses BNB. MATIC is the native token for Polygon.
MetaMask and Gas Fees
The reason gas prices are high is not due to MetaMask controlling the fees. MetaMask is just the interface to the internet of value. It is similar to how your web browser is an interface to the internet of information.
No wallet can control the gas fees on a blockchain network because its demand determines those. There is a scarce amount of space on a blockchain’s block, bided up by those who want their transactions confirmed. Currently, miners pick the fees which pay the most to maximize profit and remain incentivized to run the network.
What are Side Chains vs Layer-2?
Both sidechains and Layer-2 chains are scaling solutions to allow more transactions at a cheaper cost by offloading them from the main network. Think of them as side streets that cars can drive to reduce traffic on Main Street.
In broad terms, the difference between sidechains and layer 2 is how the network is secured. Sidechains secure their network by having their own validators or miners. That means they have greater independence and flexibility. However, depending on the number of block validators, less security.
A side note: Validators are like miners in their role of verifying network transactions. However, how the independent nodes agree on their shared state (the consensus mechanism) is Proof of Stake versus Proof of work.
Layer-2 solution latches onto the main network and leverages the main nets validators for security. This increases their security but reduces independence and customizability.
You can learn more about sidechains via EthHub and about Layer-2 via Ethereum.org.
For the more technically inclined here, hear Vitalik Buterin talk about Layer-2 solutions or read about it. Additionally, here is a post about sidechains from ethresear.ch.
Popular Custom Networks:
The most popular custom networks as of writing this (circa May 2021) are:
- Binance Smart Chain
- Polygon (MATIC)
- HECO (Huobi Eco Chain)
Please note that Polygon used to be called Matic. After the rebranded, their token is still called MATIC.
Others that are starting to see traction include:
- Avalance
- xDai
Crypto is fun! Experiment with different networks and discover new things. Ethereum is the leading and most secure network that is fast becoming the settlement network for the world.
However, due to high gas fees, many are locked out. Rather than not get in on the fun, try out new chains, including many of the Layer-2 and sidechain solutions coming out now.
In general, how do I set up custom networks?
Perhaps your custom network is not described here. That’s ok. As the ecosystem grows, more chains will come out.
Usually, you can visit a protocol’s website. They will have information on how to configure MetaMask as a custom network.
Please beware of getting this information from the project’s official website. It is possible to be connected to an imposter network and be subject to phishing or losing your funds.
What is the difference between Mainnet and Testnets?
Mainnet is where tokens have real value. Testnets are places where developers test their smart contracts. Testnet token does not have value.
Testnet tokens are given out for free via faucets. However, they are distributed in small amounts to ensure people don’t hoard them.
Avoid being tricked into thinking that your testnet tokens will convert into mainnet tokens and paying a fee.
How to Add a Custom Network on MetaMask?
Easily find the section to add Custom Networks on MetaMask like shown here.
Once you are in this section, configure the fields to the information for the Ethereum compatible blockchain network of your choice.
Please note that neither Bitcoin, Dogecoin or Cardano are NOT Etheruem compatible, so they cannot be added to MetaMask and require their own wallet.
Also, please note that Binance Smart Chain (BSC) is different from Binance Chain. Binance Smart Chain is Ethereum compatible smart contract platform and can be added. You can tell the network is BSC instead of Binance Chain since BSC addresses start with 0x (followed by the address), while Binance Chain starts with bnb (followed by the address).
How do I set up Binance Smart Chain?
For more info see their article.
Binance Smart Chain Mainnet
Network Name: Binance Smart Chain
New RPC URL: https://bsc-dataseed.binance.org/
ChainID: 56
Symbol: BNB
Block Explorer URL: https://bscscan.com
Binance Smart Chain Testnet
Network Name: Binance Smart Chain - Testnet
New RPC URL: https://data-seed-prebsc-1-s1.binance.org:8545/
ChainID: 97
Symbol: BNB
Block Explorer URL: https://testnet.bscscan.com
How do I set up Polygon (MATIC)?
For more info, see their official docs.
Polygon Mainnet
Network Name: Polygon Mainnet
New RPC URL: https://rpc-mainnet.maticvigil.com/
ChainID: 137
Symbol: MATIC
Block Explorer URL: https://explorer.matic.network/
Polygon Testnet
Network Name: Mumbai TestNet
New RPC URL: https://rpc-mumbai.maticvigil.com/
ChainID: 80001
Symbol: MATIC
Block Explorer URL: https://mumbai-explorer.matic.today/
How do I set up xDAI?
For more mainnet info, please see their official docs..
For more testnet info, please see POA’s official docs..
xDAI Mainnet
Network Name: xDai
New RPC URL: https://rpc.xdaichain.com/
ChainID: 0x64
Symbol: xDai
Block Explorer URL: xDai (xDAI) Explorer
xDAI Testnet
No Testnet is available for xDai. For testing purposes, it is recommended that developers first deploy to the POA Sokol testnet.
POA Core is an autonomous network secured by a group of trusted validators. It is essentially a separate network with its own set of validators versus using Ethereum.
Network Name: Sokol Testnet
New RPC URL: https://sokol.poa.network
ChainID: 77
Symbol: SPOA
Block Explorer URL: POA Sokol (POA) Explorer
How do I set up Avalanche?
For more mainnet info, please see their official docs.
For more testnet info, please see their official docs.
Avalanche Mainnet
Network Name: Avalanche Network
New RPC URL: https://api.avax.network/ext/bc/C/rpc
ChainID: 0xa86a
Symbol: AVAX
Block Explorer URL: https://cchain.explorer.avax.network/
Avalanche FUJI Testnet
Network Name: Avalanche FUJI C-Chain
New RPC URL: https://api.avax-test.network/ext/bc/C/rpc
ChainID: 43113
Symbol: AVAX
Block Explorer URL: https://cchain.explorer.avax-test.network
Avalanche Local Testnet (AVASH)
Network Name: Avalanche Local
New RPC URL: http://localhost:9650/ext/bc/C/rpc
ChainID: 43112
Symbol: AVAX
Block Explorer URL: N/A
How do I set up HuobiChain?
For more mainnet info, please see their official docs.
For more testnet info, please see their official docs.
HuobiChain Mainnet (International)
Network Name: HuobiChain- Mainnet
New RPC URL: https://http-mainnet.hecochain.com
ChainID: 128
Symbol: HT
Block Explorer URL: https://hecoinfo.com
HuobiChain Mainnet (Mainland China)
Network Name: HuobiChain- Mainnet (China)
New RPC URL: https://http-mainnet-node.huobichain.com
ChainID: 128
Symbol: HT
Block Explorer URL: https://hecoinfo.com
HuobiChain Testnet (International)
Network Name: HuobiChain Testnet (International)
New RPC URL: https://http-testnet.hecochain.com
ChainID: 256
Symbol: HT
Block Explorer URL: https://scan-testnet.hecochain.com
HuobiChain Testnet (Mainland China)
Network Name: HuobiChain Testnet (Mainland China)
New RPC URL: https://http-testnet.huobichain.com
ChainID: 256
Symbol: HT
Block Explorer URL: https://scan-testnet.hecochain.com
yeah it worked